I can attest for Nvidia shadowplay. It's pretty good. I'm running a 770 and with Shadowplay on it doesn't seem to drop my frames too low at all, but it all depends on your preference. You could use just the manual recording mode so you don't have both options running at the same time. I've tried manually recording and it seemed to work great except for a few hiccups (but those may have just been because of my setup.
The only bad thing about it right now is that it WILL NOT record voice input for the time being. So this means if you've got your headset and mic on it won't be picking you up talking. It does capture all outgoing sound though. So if you're talking with people on teamspeak it will capture your friends' voices, just not yours.
I think I read a blip somewhere that they are going to add voice input recording at some point as well as streaming direct to twitch.tv. Overall I think it's a great tool, but it's in beta, so there ya have it.