This somewhat depends on the compiler, linker, and interpreter. If you are using a framework that is optimized for a certain CPU then you most likely want to go for that CPU architecture.
At the assembly level, they both use the same instruction set and there isn't a distinct advantage. With C++, if you use something like Visual Studio, I found a site that performed benchmarks on Windows 8 - VS 2012 - Firefox compile. Here are the results: benchmarks. Although this shouldn't be a definitive stamp of success for Intel since it is somewhat dated, for other benchmarks you can find on that site, Intel does win in almost all cases with the i7 architecture. So although you don't really care about graphics, other applications you may run on your machine may have noticeable differences in performance in comparison.
EDIT: I've noticed the question has been updated. Because of your specific requirements choices, I would definitely go with Intel. Now, between the two if you are going to utilize multi-core processing, then the Intel Xeon E5-2620 v4 will be optimal. Looking at this link: Core i7 vs Xeon you can see that in terms of multi-core processing Xeon performs better in benchmarks.
One last thing, if price is a factor at all the Core i7-5820K can be considered over the Xeon. Just looking at a quick price check on Google between the two, the Core i7 is cheaper.
