On startup, After Effects give a warning banner recommending you buy an nVidia GPU for GPU acceleration with ray-tracing. The key word in this message is "WITH". You do NOT need an nVidia-based GPU for GPU acceleration. The "CUDA cores" that nVidia has in their cards helps out your CPU with ray-tracing 3D. By default, After Effects 3D mode is set to "Classic 3D". Cuda will NOT help with Classic 3D. Ray-tracing in After Effects is rarely used by many users, and Adobe's message on GPU selection confuses many in believing that an nVidia GPU will make their After Effects run faster. This is not true.
Since many users never will use ray-tracing, what is the point on buying an nVidia GPU especially for use with After Effects? THERE IS NO POINT. Most major plug-ins for AE are GPU accelerated, but brand does not matter. These plug-ins include but are not limited to: Sapphire, Video Copilot's Optical Flares, and Magic Bullet Looks. As a matter of fact, NOTHING that is GPU accelerated in AE requires a certain brand except for ray-tracing.
This, in conclusion, means that an AMD/ATI, Intel, OR nVidia card will speed up AE and its plugins that support it. Since I rarely use ray-tracing (all my 3D work is done in other applications) I actually ordered an AMD GPU because the price was right and it was right in that price to performance ratio that I was looking for. I will not advocate one brand over the other, as it truly depends on what GPU fits your needs (and games) best.