Basically the math works out as when you move up in the stakes, the pots double in size. Assuming your BB/100 doesn't get cut in half or worse when you move up a limit, you should play at the highest stakes your bankroll allows.

Lets say you're 'rilla and play at the 10K/20k stakes. At the 5k/10k stakes he can run the tables, making about 20BB/100, but at the 10k stakes he makes 10BB/100. He's making the same profit at both, but problably learning more at the higher limits.

For us normal players, if we make 7BB/100 at our lower limits and 4BB/100 at higher, it's more profitable and better experience to move up limits.