Not easy to compare.
I suspect twith the 50mm lens you will get around 1:1 magnification with about 5cms working distance and with the 28mm lens around 3:1 magnification with about 1 or 2 cms working distance.
So it rather depends on what magnification you want and what type of subject you are shooting.
I would like to get really close to flies, spiders and other insects but with as much working distance as possible.
I also have extension tubes if they can help.