Speedster rules
The Speedster rules in general are a slightly different system to normal, as they provide extra abilities on top of the standard. The Speedster rule gives +2 BMD to a model, which stacks with the Fast they all have to give an 8” basic move and allows them to use Speed Force powers. I personally find that the powers with no paradox, or a 6+, to be the only ones worth using in most cases, although they all have situational use. Many Brave and the Bold Speedsters also have Speed Force Master, allowing them to bank 2 of their Speed Force counters and spend them as normal counters during the turn. They are unable to be blocked unless they are attacking another Speedster, which may make them look like great beaters, however they have no bonuses to hit and are strength 4+ or less in Brave and the Bold, requiring the Muscle Growth power (1 SFC, no paradox) to get +1 strength.
Role of Speedsters
In general, Speedsters are very good at objective grabbing, due to high speed and defence, but they can hold their own in most cases. In terms of hitting, with Speed Force Master they can potentially throw out 10 unblockable attacks a turn (Fast Combo for 1SFC, 3AC and 2SFC as AC), most at 3+ strength with Muscle Growth. They are best suited to hitting weak henchmen , as they can easily hit in that case, and they shouldn't be used as dedicated attack pieces. Their basic role is to be annoying, tying up the opponent and swinging VP (by claiming yours or denying the opponents). They can shut down single guns very well through Rapid Disarm, and they can tank relatively well through some of their other powers. While they aren't as oppressive as Magic users, they can do a great job of being a piece that's hard to handle on the table, and one that shouldn't be ignored. One big thing to remember is their Too Tired! rule, where if they have no counters they are at -1 defence, and none of them have native Martial Artist so they are prone to outnumbering. With this in mind, one must avoid Enervating at all costs, and manage their counters to maximise Speedster effectiveness.
Barry Allen and Moral Compass
All versions of Barry Allen have Moral Compass as a big negative trait, meaning you cannot use the Coup de Grace rule when he is on the table and not KO. This in Brave and the Bold means you need to either maximise blood damage or arrests, preferably both at once. If you don't do this, you will likely find yourself not being able to keep models out of the game, and find the damage you do deal will be mostly average because any bigger target will just get up and keep going. It's an easy trait to play around, Gotham Policewoman being an autotake with any Flash and the Arkham Guards being great buys in general.
First up we have Kid Flash, the cheapest
Speedster option available in the game at 74 rep. His statline is somewhat
lower than many others (he’s the only one not defence 5). At willpower 6 he is
fairly standard for his points cost, and can do a good amount standard, but
it’s his traits that push it a bit better. Speed Force Master, as mentioned
before, lets him spend Speed Force counters as normal AC, so he can find
himself at effective willpower 8 in some situations.
Offensively
Bart is nothing special in terms of offence, he can put out the same amount of dice as any other BatB Speedster but at a lower strength. Where he really shines in this regard, however, is as a control piece, with his unique Speed Force power. Vibration Wave can potentially knock down a large amount of models, especially in crews with low movement henchmen, setting your crew up for whatever purpose you want. Against low agility, high defence characters, this power is incredibly useful, especially if you have first activation, because you can knock them down and negate the high defence for at least an activation. However, this power is especially unreliable, as it has a 5+ paradox and requires the opponent to fail agility rolls. I would recommend only using it when the chance of gaining VP from it is greater than any potential downside for it, because it is a risky power to pull off.
Defensively
Despite being at a lower defence than any other Speedster in the game, Bart is very effective against guns through his unique traits. Concealment means he can entirely negate ranged attacks, and even if he doesn't he's still movement 4 with Dodge, so he can reliably prevent them. At 5 endurance he is fragile, and one has to be very careful to keep counters on him so he doesn't drop to defence 3, at which point he is a big liability and quite easy to kill.
Overall
The best role for Bart is an objective sitter by far. He isn't very offensive, preferring to hit weaker henchmen if anything, and he has great tech to just sit and score. Use Change of Plans to put 2 3VP objectives together, run him in and pop Concealment, and defend.
Teen Titans
Bart also has some play into Titans, being on the team list and being a not too bad option for them. Speed Force Master lets him mitigate Inexperience, although other than being fast he doesn't do all too much otherwise (and Titans aren't lacking in fast models).
Next up is the cheapest of the Barry Allen Speedsters, TV Flash. Compared to the other Barry Allens we have, he loses out on endurance and movement, but at a significantly lower points cost. He is a sidekick, meaning he can give henchmen rerolls to Let's Go! (although he will rarely be near enough to use this) and it means he can be a Boss of a crew, meaning you don't need another character to take charge. TV Barry also has 1 lower Speed Force level when compared to the other two versions, meaning he can do less in any one turn, although this is somewhat minor.Teen Titans
Bart also has some play into Titans, being on the team list and being a not too bad option for them. Speed Force Master lets him mitigate Inexperience, although other than being fast he doesn't do all too much otherwise (and Titans aren't lacking in fast models).
Offensively
His attacking is as decidedly average as any other BatB Speedster, but the one thing he does bring is his quite good unique Speed Power. Acting as a short ranged attack that does 1 blood and 2 stun damage, it ignores almost all abilities that defend against ranged attacks (Ping! and Dodge), and at strength 3+ has a good chance of wounding. It is, however, expensive to do, costing 3 of his 5 Speed Force counters and with a 6+ Paradox by the FAQ. It is still very good despite this, just not as amazing as Ezra's ranged threat
Defensively
In terms of raw stats, he is in the middle between the other Flashes and Kid Flash. Having 1 higher defence than Kid Flash is a good probability swing, although the 1 less movement from the Flashes means he isn't dodging quite as easily. Looking at his endurance, at 6 he is right between the 5 of Kid Flash and the 7 of the others, and you're pretty much relying on not getting hit with him. The comparison with Kid Flash becomes unfavourable when you consider Concealment though, as Kid Flash can hide far easier, making TV Flash the more fragile option. Endurance 6 on a Boss is on the lower end as well for this cost, but he is still a good choice, if a little risky
Overall
All things considered, TV Flash is a good budget Barry, and the best option to have a Speedster led crew. With that said, if you are looking for a versatile Speedster who can harass at will, Ezra Miller is likely the better option in almost any case.
After the TV show Flash, now we have the one from the movie. 1 higher endurance and movement than the TV version, they otherwise share many of the same standard traits, with one major exception. This comes at an 18 point/$100 increase, although it is well worth it.
Offensively
This is where Ezra shines, but not hugely. He is still definitely best suited to attacking henchmen and other low defence models, but his attacks are slightly more effective due to his biggest ability- Mixed Combat Style. This allows him (with the right Speed Force powers) to shoot a target with his Kinetic Lightning, then move into combat with any model he can reach and hit them with 10 dice at strength 3+. In terms of raw potential, it is excellent, although no bonuses to hit and potential to dodge the Kinetic Lightning means he is a henchman bully, being able to act with near impunity on them. All his attacks have the Electric trait as well, meaning if he crits the opponent is stunned, leaving them completely shut down for that turn (and usually a safe ignore). His Kinetic Lightning is a Beam, so pings are only on a 6+ against it, but at 2+ strength blood stun the RoF2 is decent enough to harass a great deal of models, especially if Electric triggers.
Defensively
There isn't much to say here, a defence 5 movement 5 model with Dodge speaks for itself. He lacks any specific defensive abilities, but he has enough in raw stats to take a good investment to take out.
Overall
I definitely believe Ezra Flash is the best Speedster in the game, although like all the Flashes the list needs to facilitate him. He is still a great harassment piece, and I feel like everyone should have him as an option in their toolkit.
Last, and probably least, is the comic Flash. The first one released, he has the same statline as Ezra except for 1 higher willpower, and the same traits as both other versions of Barry. This comes at the steep cost of 125 rep, which is not all that incredible when the other Flashes are considered, and unfortunately almost never worth it when other options crew wide are factored in.
Offensively
There is really nothing to cry home about here, he is exactly the same as TV Flash and Ezra, but without any fancy ranged ability or Electric to spice things up.
Defensively
Again, he is the same as Ezra in every regard here, so nothing really special.
Overall
It is probably obvious by now, I am not a fan of this model. I used him pretty heavily when 2nd ed first released, having great success as a boss, but now that Ezra is out I rarely take him. In terms of a crew leader, he is more valuable than TV Flash because he is more survivable, but at the cost of another solid body on the table (one with Arrest to mitigate Moral Compass somewhat) it is a hard choice to make.
EDIT: New TV Flash
With the latest set of releases, we got a new version of TV Flash. All in all he hasn't changed much, but the changes that did get made are quite good. His stat line is identical, as is his unique power, but for the same cost he has now gained Arrest. This helps him a lot in getting around Moral Compass, so is a really great addition to the character.