There are many reasons to prefer the Mac. But in this comparison, you also have to consider that it probably not only has the better CPU (the iMac is overdue for an update with a more current CPU) and the better Graphics card, but the advantage that you can change grapics card and SSD easily any time you feel like doing so.

I do think that the upper range iMac is one of the best value Macs, but it still suffers from being glued together.