I read everywhere that render farms have dual Xeon processors with some 30-odd cores to render complex scenes, but I also read about powerful workstations that contained a rendering GPU like something a Quadro.
My question is, which one actually performs better in Cycles? And what will surpass my overclocked 980Ti? (I will do rendering benchmarks if you wish)
I use Blender at work. This might help you out.
My work computer used to be a Mac Pro with a hyper-threaded Xeon processor. It was a little older, like from 2010, but it could run 16 simultaneous threads. That translated to 16 little squares rendering at the same time in Cycles.
A year and a half ago I asked my boss if I could build a PC instead of getting a new Mac Pro. They approved and gave me a budget of \$3500, roughly the amount a new Mac Pro would have cost. Because I was choosing my components I bought two GTX 980s (they were about \$550 a piece, so \$1100 total).
When I compared the Cycles rendering speed on the two computers, the PC I built rendered the same scene SIXTY TIMES FASTER than the Mac Pro with the Xeon processor. That meant projects that used to take multiple week to render would now be done over night.
I used Render.st once. It was a very smooth experience, and didn't cost me anything because they had given me a \$25 credit to get started. It wasn't blazing fast, but it did render for much less money than the cost of building and maintaining my computer. And like Pyroglyph mentioned, all the frames began and ended around the same time.
If you are rendering things every now and then, for fun, I suggest trying a render service like Render.st. It's very easy to set up.
I realize I'm coming a bit late to the party, but I've just noticed the thread and I'd like to make a couple of comments:
NVidia has 3 lines of GPUs : GTX (consumer cards, targeted towards gaming), Quadro (targeted towards CAD professionals) and Tesla (GPU processors for HPC). For Cycles, you'll definitely get the best bang for the buck with a card from the GTX line. However, if you're working on very complex projects, high-end CPUs may perform better. There are a number of reasons for which this could be happening, like for instance parts of the rendering code not being optimized enough for GPU (take volumetrics for example) and the actual way the computing process works at a GPU level. You can see the Blender Institute benchmarks on a number of systems here if you're interested in comparing results. And I've seen situations in which our dual Xeon servers performed far better than our quad GPU ones. So my advice to anyone looking to buy hardware would be to keep in mind the complexity of the projects you'll be working on.
Regarding the way a render farm works, the hardware we're rendering on at RenderStreet is pretty fast - both the CPU and the GPU servers. But the true power of the farm is that we're able to throw dozens or hundreds of identical servers at your projects and render in a couple of hours what you would render in a few weeks on one machine.
And lastly, using a farm isn't that expensive, either. For instance, the price Tim mentioned for one GTX card can buy 11 months of unlimited rendering, and that's a lot of crunching power. Plus, it's available from anywhere you are traveling, with the only requirement being a decent internet connection.
Check out this page for GPU render performance Benchmarks across some popular 3D Software Render Engines. It doesn't Include Cycles, but gives a good comparison of how the currently modern GPUs rank
Dual Xeon wouldn't be the way to go for cycles, as this Render Engine is heavily GPU optimized. If you were to go CPU-Rendering style, I would recommend a Threadripper, as these have much better Render Performance per Cost. There is a good overview here for best CPUs for rendering.
