First there was no 3770s 2013 21.5 iMac. There was a 2012 system which was just a 3.4GHz I7-3770 as you can see here [https://everymac.com/ultimate-mac-lookup/?search_keywords=iMac13,2|iMac13,2] and here's the 2013 systems [https://everymac.com/ultimate-mac-lookup/?search_keywords=iMac14,3|iMac14,3] which does have a I7-4770S.
So where does that leave us? Not sure why you are down grading your system CPU. If we compare the performance of these two CPU's the I7-4770S is the better CPU and the 2013 system also offers the better GPU
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