Upgrade CPU or GPU?

Lachlan_5

Reputable
Apr 20, 2016
6
0
4,510
I am looking to increase performance of my PC to get higher fps in newer games.

I have:
GTX 970 4GB
8GB ram
i5 4670 3.40GHz
Motherboard: ASUS H81M-PLUS

I was thinking of upgrading to a GTX 1070, or upgrading my cpu.
Which would increase performance more?