Tonight I was involved in a hand that will help illustrate some of the differences. We were deep in the big $11R with about 100 left. Blinds were 3.5k/7k and average stack was about 120k. It was folded to the cutoff who raised to 17k. Folded to me in the Big Blind and I went all-in for 80k with A4. The cutoff (100k stack) thought for a long time before calling me with Q8. Needless to say the flop was QT2 and I was out. I am certain that the same player in a live tournament would have folded his hand, so why did he call me here?
There are a few reasons. Firstly, given the availability and frequency of online poker tournaments the player was probably playing many tables and didn't consider it to be a disaster if he busted one of his tournaments, he still had many other tournaments he could play if he wished. In a live tournament, when you bust you have to go home or maybe play cash, either way you cannot get your buzz of tournament action until another night. Therefore people guard their tournament life more carefully than they do online.
Secondly live tournaments are played tighter than online tournaments, partly because people guard their chips more heavily as mentioned above. This means that my all-in range in his eyes in a live tournament is much tighter and he is much more likely to be dominated. Whereas online, where aggression is king, he probably assumed that my range was wide and he was unlikely to be dominated. Therefore he figured he was getting nearly a fair price to call based on pot odds.
A third reason he would not call in a live tournament but will online is because there are consequences to calling with Q8 in a live card room that do not exist online. If you make this call playing live with questionable pot odds you will be branded a fish by the rest of the table, you will make the person you called very angry, and you will be embarrassed to show your cards. This creates an uncomfortable situation that players will simply avoid by folding the Q8 when it is a marginal decision. None of this happens online of course, you can simply call and gamble if you want to and relax in complete anonymity.
A fourth reason he calls here is because most online players are happy to gamble with the worst hand in order to accumulate a big stack because they see it as their best chance of beating a large field. There are ten times as many runners in online tournaments than live. Because of this people try to gamble in spots to accumulate chips which they can use to bully shorter stacks. A big stack allows a player to progress more smoothly than if they were short stacked. The average good player is happy to finish in 45th place gambling with the worst hand to get a big stack as opposed to making sure they make the final 18 if it means they will be most likely be short stacked. This is an understandable strategy given how top heavy prize structures are, and the advantage gained for a good player if he has a big chip stack with not many players left.
Because of these reasons there is a higher degree of luck in online tournaments than live. The fact that I am willing to make this statement is probably an indication that I am more of a live player than online. Also I tend to enjoy the experience of playing live more than online in most situations. However I have made more money playing online than live over the last two years, and it is something I take more seriously in terms of BRM and volume. So it is hard to answer the initial question one way or another, online or live? Maybe it's just that I am a rare breed of the two: an onlive player.