What's Better: One Large PC or Many Small Ones? Okay, so I'm working on setting up a small render farm, and I'm unsure of something. Is it better to use one really powerful computer, or the price equivalent of smaller computers in an array? 

I'm a student and my teacher asked me to look into this. We have a lot of students that use blender. We use GTX 1080s for rendering, but for those of us that do animations, they often take a while to render. We have a server system running and it wouldn't be difficult for us to set up a network rendering machine or a render farm. But I'm trying to figure out if it's better for the single powerful machine, or multiple small machines. I haven't been able to find any direct comparisons between the performance differences of those setups.
I agree with Duarte that there is no universal good answer for this. In fact the real answer will depend on what time you ask this e.g. the GTX 10 series brought in a swathe of cheap GPU power where [1] a GTX 1060 is the best bang for your buck in terms of FLOPS/$.

Just bear in mind that if you do decide to opt for a bunch of smaller gpus, the amount of onboard memory will limit the size and complexity of your blender scene.

If you are looking to drastically reduce render times, check out airenderer.com. I used it a couple of times, it is good for most scenes and they claim can reduce your render times by up to 97%...[2] it is more like 90% but still very good.

sources:
[1] geforce.com official FLOPS versus RRP
[2] airenderer.com