Since I am a NL player, it makes sense that I recommend NL. If your hourly rate is strong then stick at it. You can only get better and can move up to even bigger games faster if you choose. Eventually you can make great money at both, but just for the sake of it the time spent 'relearning' limit, I'd stick with what I'm good at.

I have one guy buddylisted at party who play 2K NL all the time, up to 8 tables at a time. Although I have no proof (don't datamine), I'm sure he's making a killing.