You're right about price/performance but for some its more than that. I had a crossfired 7970 config and switched to a 780ti which is probably a downgrade in performance but I would have switched teams years ago if I knew how pleasant it was to use Nvidias software, their GPU boost, shadowplay, optimisations etc, their shit just works. Sure AMD have the similar features on raptr, but have you ever used that shit? Raptr is an atrocious buggy piece of shit (from my experiences). I should have made a list of all the bizzare things that happened with that software, ill try remember a few.
Metro LL when running Raptr the mouse would not be constraint to one monitor, aiming to the right would mean my mouse drags onto my secondary monitor, then clicking minimizes to the desktop.
Splintercell blacklist, when Raptr was running I could see the screen refresh and flash white, like some crazy seizure inducing shit.
Borderlands, game would just crash upon launch when Raptr was running.
Theres heaps more but I cant think of all of them, but all of them were persistent, and fixed by just killing Raptr and running the game again.
As for Catalyst Control Center only problem there was that presets only remember screen positions and not things like gamma. And yes the cards were loud, hot and had coil whine.