it really does not matter. The difference is not whether you can make $$$$ or $, it's more about how you want to play.
You will finds strong MTT/cash players at high limits ad fish micros (obvsl.) so if you want to get easy money it will be more about getting better at your game than at finding a variant.
For exmp. micro MTTs are filled with fish !BUT!, MTTs have bigger varience than cash; cash are usually filled with good players !BUT! micros are filled with fish that will pull 2 pair for 3 streets, and even if you get owned by varience you lose a few BI and not your MTT life, that being said at MTTs you can turn 3$ in to 300$... i hope you see my points =)