I have not played live a lot yet so I took the last option.
From a nuts and bolts perspective, online is easier because it gives you all the chip counts and whatnot. First time I played live I was confused, the game seemed to go SO fast I was missing my turn had to ask questions of things I should have known, etc. And I was concentrating!!

I was also nervous though, and that didn't help.
I really think that it is difficult to compare the two though, they are just different. I tend to play a good game more consistently at live games because I focus 100%. I don't have any other potential distractions (phone/daughter/door ... dog and cats!). I also feel a lot more competitive when I'm actually sitting at a table. At the same time, if I play somewhere I haven't played before ... because I haven't played a lot of live ...
I still get nervous.
Tells are the other thing ... if you give them away and you can't pick them up - you're going to do better online! If you don't give them away and you can pick them up that's a big advantage and live is going to be easier for you.