Watching a live stream of gameplay, the guy said the Carb SMG rocks. So, I check out the stats of SMG.
http://brink.wikia.com/wiki/Weapons

CARB-9 has the highest damage and largest magazine size.
Even with the longest reload time, it seems to be the best SMG, far better than the other SMG.
I guess most player will use the same SMG, which is boring......

Technically the Tampa would be the best on paper as it's 22 damage to the CARB's 23, but has no burst delay and twice as fast reload.

I don't see how bust delay affect the output of the gun indeed in the live stream. May be I have no idea what it is.....

For the reload time, let's say I need to shoot 90 bullets. For CARB, I need to reload once, for 2 sec. For Tampa, I need to reload for two times, which is 2.4 second.
Also, a default larger magazine is always better in CQB.

It has a slow ROF though. Some people like more damage and lower ROF while some people like the highest ROF possible and dont care about the dmg. I wont write any weapon off as being overused until this game has at least been out a cpl of weeks and people have been able to actually try them all out.

The ROF of all SMG are the same in the stat chart. I just hope CARB won't be an OP SMG.

TAMPA FTW. Try reloading in a tight squeeze and it takes forever . . .you'll have to keep switching to your secondary. . .

I don't like how TAMPA look indeed, lol.
Hipfire seems so accurate.