EVE New Citizens Q&A

http://eve-marketdata.com/station.php?step=Rank is my source. More specifically, my memory of what that site said (which is why I didn't pick up the considerable falloff in activity in Oursulaert).

Volume of sell orders may not be an absolutely perfect metric but it does tell you a lot. Daily turnover would be better but is harder to measure and also would favor Jita over other hubs due to Jita being the place large speculative holdings tend to be stored. (For instance if someone bought a half trillion units of Tritanium, or two thousand units of PLEX, with the intention of holding six months then selling, their stock would be in Jita and would turn over there).

All of the true hubs will allow you to fit any subcapital fit you want as long as you aren't intending to fit officer modules and are occasionally willing to substitiute for low-demand modules/rigs that might be out of stock at a given time (for instance, tech 2 CPU rigs may not be available).