As a StormDroid dev, i am obligated to get you to at least try StormDroid. HOWEVER, when it comes right down to it, its all about what you want in a ROM. Both ROMs are debloated, run great, have good battery life, exceptional performance, and overall ROCk. BUT, Velocity is no longer being developed. 1.2 is near perfect as is, but StormDroid will see many new iterations, and is still extremely active. on the other hand, however, with velocity, you get Savoxis' AWESOME velocity script backend. all in all, the ROMs really tie in terms of which is the best. You should give them both a try! If you so feel inclined, you could even purchase Boot Manager, which would allow you to have multiple ROMs on a single phone! [market link]
A few notes: i can OC higher on Stormdroid, but my battery life is better on velocity. YMMV, of course, and i strongly suggest you give both a shot. hope i helped!
J2