Bluffing works best in live poker against good players. Bad players can't be bluffed online or live as a general rule. The tells are fewer online as well. All in all online poker is good for practice or fattening your bankroll.
In my opinion it's a video game when played online.
Poker is a...
Live poker for a myriad of reasons. A few being physical tells, which are not available online. That is the most important as poker is a game of people as much as it is cards. Online isn't even close. It's more of poker turned to video game. Also, I enjoy playing with my chips at the table. :)