While I can't speak from recent experience, my past usage of GFE (before sign-in requirement) was nice enough. If it was still possible to use without sign-in, I'd probably stay with NV. If you are planning to primarily use the control panel, I'd think twice though (it isn't just slow to load, but painfully slow to use). It is one of those things where you can tell the CEO of a company no longer uses its products because if he/she did it would never make it to public in the first place, and if it did make it public the people responsible would probably be fired quick, fast, and in a hurry. Both companies have issues with various games, so you may want to research the specific titles you are planning to play for any ongoing/long-term issues.
EDIT: Just out of curiosity, I logged into GFE, and it doesn't even work properly. No global settings that I can find and all the per-game pages show "Unable to retrieve settings. Try again later." I'll tell you what I am going to "try again later", an AMD card.
EDIT2: Finally the settings for the few games it detected appeared. Of note, there are 2 copies of one game which display different settings, and you can't actually change the settings unless you let NV apply one of their cookie cutter "optimized" presets, so it is useless garbage. The only potential use for it that I can see is the recording/streaming functions, but I'd rather use OBS for that. So back to useless garbage which you have to sign in for. I'll pass.