Settling a debate, online vs. live skills

[damaniac]

A couple of friends and I had a disagreement over the likelihood of a player being mediocre online but excellent live, or vice versa.

Essentially, my friends claim that while someone could be mediocre online (mediocre could be read as a small loser to a small winner at a given level, perhaps), they could well be a top-notch player live at comparable levels (where comparable refers to the skill of the opponents and not the amount, so comparing 5/10 online with 15/30 live or whatever it most likely corresponds to). Their reasoning was that they could use tells that are unavailable to online player.

I countered that, while there are somewhat different skill-sets necessary in making reads online vs. live, behavior tells are only going to form a small part of that most of the time. Furthermore, if a player is mediocre at online poker, and thus probably either has a flawed understanding of some basic poker concepts, or just some bad leaks in his game, those are going to carry over into live poker, and you are basically not going to be able to make up more than a small fraction of your mistakes through tells.

However I'm mostly speculating on this as I've never really played above 5/10, and neither have they. So, to those of you who have put in many hours at both types of games, or just know more about this than me, who is right? What other factors might apply?