Retina really refers to perception of the number of screen, so it depends on how far away from your monitor you sit. Displays which are used from a close distance require a much higher PPI to be "retina" than displays used at a distance. A 1080p TV can be a retina display if it's far enough away.
All commercially affordable 27" monitors are the same resolution, the main difference would be in the coating/etc, which would impact how the monitor seems in various ways, and that depends on preferences as much as anything else, as well as use cases.