I found Win 7 (pro) and Win 10 (pro) were functionally very similar. Win 7 will get security updates until 2020, Win 10 until 2025, so the main benefit is that extension. But who knows how Win 10 will change during that time?

If you value the stability of your system I would stick with Win 7.

Though personally I prefer the look and feel of Win 10 (but I don't actually use it - I just maintain it.)