Being that I mine on NiceHash with nVIDIA cards I can't use the auto-switching feature because the best nVIDIA mining tools (ccminer and cudaminer) don't support it.  To that end, I've come up with a Windows Program, Nice Hash Control which can start and stop mining apps based on which one is currently most profitable.  Hope this helps, and please send a few mBTC my way if you find it useful.

http://stuffofinterest.com/NiceHashControl/NiceHashControl-1.0.0.png

BTW, the recent ccminer 1.2 release made for a nice bump in earnings on X11 and X13. Screen shot above is what I'm getting with two GTX 750 Ti cards.