Well, if it's just these two for the moment, it's a clear recommendation for the i7 version, simply because only the i7, as far as I'm aware of, supports hyper threading (virtual doubling of available cores). Since both of these Nucs don't have that high a clock frequency, the hyper threading will definitely have a big impact since your rendering program can use 8 instead of just 4 threads. Rendering is one of the prime areas where hyper threading gives you a real benefit of this technology.
The other, general, question is what you're really aiming for with the NUC. Do you want to render high-resolution, real-life like renders with it? Then, honestly, you'll have to plan for a lot of waiting time with just 2,7 GHz base frequency (although the 4,5 GHz Turbo speed aren't that bad, but I don't know how long a NUC can keep that speed before it's overheating).
If you just want to do an occasional render with Blender or Keyshot, the i7 NUC is definitely more than enough. And if it's really just a couple of renders a week, it might even be enough to go with the i5, save a good deal of money and just keep it running while you do other things. I went back to an i5 with my last computer upgrade (many years ago) since I wasn't rendering that much anymore and wanted a better game performance and less energy consumpter rather than the i7 hyper threading. But it really depends on what the machine is mainly used for.
The only thing I cannot answer is how the onboard graphics will interfere in the process. The GPU is NOT needed for the actual rendering process, but it is needed to display your changes while setting up scenes. So depending on which program(s) you use and whether or not they have inbuilt preview options, you might run into a bottleneck at this end. But again it depends whether or not you're planing to regularly build/adapt new scenes. However, even in this case it should be possible to add an external GPU to the NUC in case you need that extra graphical power.

GPGSL : Team Owner of 'Maverick Track Performance' (MTP)