That’s true to some degree. NVIDIA drivers have a better track record and they offer CUDA, which some applications can take advantage of.
Blender supports GPU-accelerated raytracing with Cycles using both CUDA and OpenCL (which is the “open” alternative to CUDA). There was a lot of trouble with OpenCL drivers on AMD, but the situation is slowly improving. You might soon be able to render with OpenCL on AMD, more-or-less fully-featured.
I love radeon’s warm color and smooth perfomance with movies, old geforce I used was very fast but its color was kinda artificial.
I don’t know when you last did this comparison, but these days all GPUs output digital signals (via HDMI, DisplayPort and DVI) and there is no difference whatsoever in the colors (assuming you use the same color profiles).
There are still people who claim there is a difference. There really isn’t. Either they’re suggestible and see things that don’t exist, or they had their color calibrated and the settings were lost when they switched GPUs.
Anyway, getting a “warmer” or “colder” look is something you can easily configure for yourself.
If you want to play it “safe”, get an NVIDIA card. If you want to do GPU rendering and want to gamble on AMD/OpenCL support improving, you might want to consider an AMD card for better value (e.g. the 390/390X offer 8GB of VRAM for a fairly low price).