Since I'm Philly-stay-at-home-no-mates, I'll have to take everyone's word for it.
But it makes sense to me that playing with a band is far, far better than playing on your own. It's all about interacting with other people, isn't it? And does it really matter if you're not practising at home? OK, maybe your sweep-picking technique will suffer, but surely you learn far more useful stuff from playing with other musicians.
What about the aspect of playing for an audience? Presumably that extra pressure (and adulation :P ) gives even more of a buzz?