really depends on the games your play for stuff like BF4 you should probably get the 980 if you want max settings if not go for the 970

I would suggest going online and looking at some benchmarks for each card. Seeing as they're both some of the most popular GPU'S out there there's literally hundreds of benchmarks out there. Obviously to take full advantage of a 144Hz monitor you're gonna want to be running games at well over 60FPS. With decent settings I don't know if you'll be able to run modern triple A games at those framerates, at least not with a single one of either of those cards, unfortunately. But if you're looking at playing some less demanding games like LoL and so on, then rock on! Good luck.