During training you will meet some friends for life but having not got a flying job yet means I'm not best placed to comment on the social life after training. There were enough opportunities to party whilst training (to a greater or lesser degree depending on your ability in the classroom and the bar!) but if you're looking to "live a little" whilst you're still young enough I would say go to university. Not only do you get a great social life but apparently amongst all the drunken debauchery they even dish out degree's which means you have something to fall back on should the pilot option go nipples-up.
Knowing a few pilots under 25 I can safely say that on balance I have a far more active social life than them right now whilst working my 9-5 office job. It amazes me that one of them has so much going for him yet can't even pull a burd - apparently pilots are highly sought after property by the opposite sex - another myth destroyed! There is a lot of work involved once you get a flying job - type rating, line checks, killer shift patterns and much more besides which all transpire to make partying rather difficult for those I know who do airline flying. Obviously hangovers ain't tollerated on the flight deck but in the office it's hardly an issue.
Go to Uni.
VFE.