I make a good deal of my money playing HU, and I believe that the level of play for nl is much lower than in limit, at least for HU. The nl players are SO undisciplined, as an example, I won 4 HU sngs in a row within 12 minutes because people have no concept of how to use their chips. Even playing against a COMPLETE idiot in limit, it takes 20-30 mins to beat them out.

In general, I prefer playin nl when I'm at the top of my game and a limit game (preferably a split pot game) when my game is off to keep myself in check.