Okay, I currently own a 2 bass drum Export set, which I upgraded from my previous one drum tama
Pro; It looks cooler.
Con; If you planning on heavy gigging, prepare for a work out.
Pro; when the two are tuned similarly, the subtle differences make your overall sound much bigger.
Con; you have to tune two bass drums.
Pro; if you have a decent double bass pedal, you should be able to easily convert it to and fro to allow you either one or two drums, eg: versatility.
Con; extra drum $, extra heads $, extra gig bag$.
Pro; isolating your left foot to its own drum feels alot more natural than most remote left pedals.
Con; sound guys hate you for using more channels, stands and mics at gigs.
Pro; it looks way cool.
In conclusion, If you are a begginer, not gigging much, just like showing off to your friends and jamming like crazy, then get the other drum and enjoy it.
If you are intermediate, pushing your band like mad, gigging every chance god gives you and whoring your kit around like Paris Hilton, go back to one drum and save yourself the grief.
And if you have finally managed to make a decent living out of drumming, odds are you're an overnight millionaire and you don't have to give a f**k what size your kit is. That's your tech's problem.