Online and live are quite different in many ways. The only true similarity IMO is that a 52 card deck is used ...
I started playing live in '69 and still prefer playing live over online. The obvious advantage of online is that it is available 24/7/365 worldwide. When you're awake at 3am and can't sleep, it's daytime elsewhere and a game is just starting.
For the most part, I enjoy live much more than online. Real people playing poker is much preferred over anonymous computer ID's and avatars. I save my serious play for casino tables ... always have, always will. Playing live I seem to find that players come to the table to stay, and play, limited only to their bankroll or avail time. They don't yo-yo in and out like they do online playing hit n run, multi-tabling, sitting out, or being anonymous ... playing lukbox and maniac poker.
Online poker offers table action for pennies and nickels, or simply just for the fun of it. There are no 'fun' tables in a casino and no .01/.02 nlhe table games. Imagine going to the casino and dumping your penny stash from your piggybank on the felt as your buy-in. Unless it is a compensation game for players with regular paying play tracked, there are no casino 'freerolls'. People don't flock to a casino table by the thousands shouting "I wanza pley pokahz, gimme zum kardz, I iz ahll-een".
You have to understand that at the low and micro limits, online poker is more about the entertainment and has to be valued accordingly. LIVE poker starts at $1/$2 IF you can find that anymore and is usually higher with a minimum buy-in for one table. Serious online pro/semi-pro players don't play the .01/.02 tables for profit. NO live player multi-tables for .02/.05 cents.
I don't play as much online as I used to ... mostly because of the ridiculous play at low and micro limits. Watching villains push all-in with 5,8o just for kicks and the adrenalin rush of the win gets old and tiresome. Sure, I could deposit online and go to the bigger buy-ins but it still isn't the same as live. When I sit down with a $100 chip rack and a few bills standing behind it (table stakes), it just has the FEEL of real poker, facing REAL people who are there for one thing ... playing poker at one table.
If you ever try playing live, you'll understand the difference. But you really need to experience it to understand it fully.