Other than the obvious spektrum optimized thing, I'm not sure. I do know that I run the original non-spektrum GTB in my SC10 with my Spektrum radio and it works just peachy.

Unless you're racing at a high level of competition, I it being necessary to spend the extra money on the optimized version.

Here's the ESC chart from Novak's site that shows all the specs for both of 'em.

http://www.teamnovak.com/products/es...spec_chart.htm

Here's Novak's description of the Spektrum Optimized version:

http://www.teamnovak.com/products/es...rum/index.html

Seems that it has faster switching MOSFETs or whatever... runs cooler.