Two cabs are gonna be more versatile than one. You sound like a young guy, but if youre also the type that doesn't mind carrying stuff...you should probably start with a single 212 cab. Get a matched second one if you really think you need it.
I play the kind of music where my decision was a 112 cab. I like to travel light, I dont even carry an ipod to the gym. When the situation mandates a second 112, I will get another. I have yet to play my first gig on bass though.
Ibanez Prestige 3006E * Genz Benz 3.0 * GK Neo II 112 * blonde Englehardt upright