Comment: Whoa there. You're plainly wrong. (Score 1) 158
CUDA was released, supported by NVIDIA GPUs, in early 2007. The first OpenCL specification was not released until late 2008 (OpenCL has not been around for 4 years, as you claim). As for which is more popular, I'm afraid that you have this backwards too. The dominant market force for GPU computing is supercomputing. How many of the top 5 supercomputers used AMD GPUs? Zero. How many use NVIDIA GPUs? Three. And they're all using CUDA because it's more feature rich---it can do fancy things like direct memory copies between infiniband interconnects and GPU memory.
FYI: OpenCL on NVIDIA is implemented on top of CUDA, so you're still using CUDA if you're using OpenCL on NVIDIA.