Disclaimer: I work at Nvidia, so can’t claim to be objective in this discussion, but wanted to explain a few things.
CUDA is Nvidia’s technology for programming GPUs. Depending on your task, the programmable CUDA cores on our processor can be used for real -time OpenGL or DirectX display of 3D and 2D graphics on monitors - drawing pixels, to put it simply. This is the basic functionality of all graphics cards, and can even be handled, at a very basic level, by the integrated graphics on some CPUs. the differences become apparent at high resolutions, with complicated data sets, and in the subtle details, such as texture display and antialiasing, and rendering of shadows and ambient occlusion.
However, CUDA is also used to reprogram the cores to perform general computational processing tasks, like ray tracing with GPU-accelerated renderers, such as Octane, or NVIDIA Iray. It can also be used for other computation, such as accelerating many parts of the Adobe video production pipeline (e.g., Mercury Engine). CUDA runs on ALL recent Nvidia GPUs…
OpenCL is an open source API for programming GPUs, sometimes used used by developers supporting AMD or the Mac OS. It also works fine on NVIDIA GPUs. I won’t compare, except to note that Otoy (Octane), The Chaos Group (V-Ray), Redshift, Adobe, etc, actively develop in CUDA, but not OpenCL. They have many good reasons.
I suggest you visit Nvidia.com and check out Iray for Rhino, as you contemplate your choices. As a 3D visual effects artist and designer, having worked for two decades with nearly every renderer you can name, I can say with confidence that GPU-accelerated Ray tracing will forever change the way you think about and use rendering. You won’t regret buying the best , highest-end GPU you can afford. More CUDA cores and more memory will mean more time creating, and lest time waiting. If it were me, my choice of renderer would very strongly influence my choice of graphics card.
There is more to the decision than graphics. Much of the work that goes into Quadro is focused on improving the user experience through driver improvements, and working with software developers, such as McNeel, to optimize and certify performance and functionality. it also includes development of useful features, such as highly customizable multi-display configurations.
Finally, as for gaming, for a given GPU processor, Quadro is clocked somewhat more conservatively, to improve stability, reliability, and longevity, as these are core values for most professional users. If you really want an overclocked card for raw gaming speed, by all means buy one. It will probably work fine, most of the time, for Rhino, as well. If it’s an Nvidia GPU, it will work with CUDA, too. However, only Quadro will give you the confidence of knowing the card has been certified by software developers to reliably run their professional design applications, year after year, and that it has the support of a team deeply committed to improving the experience of professional designers.