is the 4k imac worth it?

Basically I want to find out if the 2017 4K iMac is worth it or do I just go with the 1080p one??

Sorry, but that's your decision to make, not ours. You've provided no information on your criteria.

After switching to the Retina display I will never go back. The readability of fonts is much better in my opinion, and photo's look great. As Kappy said, you didn't say what you'd be using it for, so without that information it's difficult to provide a recommendation.