not a fain of either picks.
first off the 29UC88 is a freesync monitor, which is amd tech and not compatible with your 1080. you have a nvidia card. nvidia uses gsync. otherwise its not a bad option.
4k is still not great with a single graphics card. it requires too much power. 1440p is the highest you should go with a single 1080 for enjoyable, smooth game play.