Depending on how you configure them, performance between the Mini and the iMac will be similar. To me, the decision comes down to your workflow and whether or not you will be content with a 24" display. I used a few different 27" iMacs over the years and tried a 24" when they first came out. After a few months, I sold it and went back to the 27". My current setup is a Mac Studio with two ASDs. If you work "full screen" the 24" is probably fine. For me, going side-by-side with the 24" was not a good experience.