Not a huge fan of the Sidewinder series escs Castle really gimped the becs in them 5v @2a. Even the Hobbywing 10BL50 has a 6v 3a bec in it. It's almost like they are forcing people to have to buy their external becs. The Max10 imho is a much better esc than the Sidewinder is. If you are going to...
I ran my Stampede 2wd on the Hobbywing 10BL50 esc for well over a year and it never even broke a sweat. So the standard Max10 will be plenty for a 2wd Slash or Rustler.