I prefer online. Not only can you gamble in the comfort of home , but you can play multiple tables . On the sites I use I have notes on my opponents that give me a edge on my rivals .
If you know how to play at least a little and know your opponents - a live game is much more interesting and profitable. But it is not available everywhere. Or only a cheap cache is available. Online gives more options and is available almost everywhere.
For me at least the table banter is much more positive (not that there aren't issues) and you can truly pick up information from the other players that a statistical anaylsis simply can't provide you with. Also, for the stakes I think the games are much softer. 2/3 live games are much easier than a .5/.10 game online in my opinion. Throw in the complimentary beverages and rooms, and i'm completely sold!
I still do both however and feel that they each improve my game for each other.
I have only played live once as there isn't any close to me but if there I was I would play more often. I would still play online poker but not as much as I do at the moment.
Live poker is funny to play, played it with friends, but more i prefer to play online, because you don't need to control your emotions, you can do all what you want. But in real life is harder to play- more stressful i guess.
The gap between level of play online and live is incredible and seem to be ever increasing...
-If you were beating a local casino game you should literally divide by 5 choosing the stakes you could attack online today, that is how much you should be careful.
That is from my still modest but growing live poker experience. Last few years i played ~a dozen of tournaments/festivals across Europe and in my country, and at almost all of them i played cash games as well. And i play(ed) almost all sites/ networks regularly online. And they say that in US it's even a better party at live tables, since Black Friday...
In india live poker can get you arrested except in a couple of places like goa I believe. Online poker is best and helps you to relax. Playing LIVE is good when travelling to UK & USA. USA casinos are lot better I believe especially in vegas. Also wsop is happening in las vegas from next month. Lots of games......