In my experience, limit hold'em tournaments tend to be harder to beat than NL. Once the stakes rise, you're really at the mercy of the cards. You can't be as conservative as in NL, because you won't have as many opportunities to double up. On the other hand, you most likely can't push someone you know is drawing out of a pot (or even better give him a chance to call a bet not justified by the pot odds).

In general, Sklansky's "Gap Concept" applies more than ever in limit. Preflop, play your hands strongly if no one has opened, and get the hell out of the pot if anyone shows aggression and you don't have a great hand.

For the record, I'm not saying a good player can't beat a limit tournament. I'm just saying his ROI is likely to be much lower than in no limit, where he has many more tools at his disposal.