I would prefer playing live more but the reason I play online more is simple. I can afford it. My nearest card room is now 1 1/2 hourss away and most tournaments are over $100.00 to play. I can play anytime I want with in moments at and buy in I can afford. Do I love online poker, Yes I do. Playing live is just more fun.
Online poker is much cheaper to play and you can play from any place at any time as far as you have internet and device which can run the client. It is much easier and cheaper to squeeze into your schedule one or two hours of poker play at time selected by you than it is to go to real casino and spend at least few hours in travel and play. Saying that experience in the real casino is much more fun and i like it more but i definitely play much more frequently online due to the convenience ans low cost.
the speed of the game and that you can play many tournaments at the same time, the comfort of being at home, being able to organize your surroundings to your liking to have a good session, etc. I think there are many positive things