A year or 2 back, it would be a valid point. But now, that i5 might as well be an i3 if you judge by the 8th gen.
Either way, with a 1050ti, either one will work. I'm just thinking your are seeing more games demanding more cores and I think that will be a trend that will continue as Xbox one and PS4 are both 8 core I think. So I would imagine any ports would want more cores.
I think I read even the i7 2600 shouldn't bottleneck a GTX 1070 to bad. Either way, it's not my money to spend. The i5 isn't a bad CPU, but if it's something I were getting to keep a couple of years or so, I'd go with the i7 personally.