TESTED with Photoshop: 2017 iMac 5K vs 2015 iMac 5K
View iMac 5K at B&H Photo and see also MPG’s computer gear wishlist. Not sure which Mac to get or how to configure it? Consult with MPG.
See the MPG review of the 2017 iMac 5K.
The 2017 iMac 5K shows healthy gains over the 2015 iMac 5K and the fastest possible 2013 Mac Pro lags in many areas.
2017 iMac 5K: Photoshop Filters
Apple has done a very nice job of making the 2017 iMac 5K a clear-cut win over the 2015 model, excepting perhaps the small I/O performance of the SSD.

Photoshop Filters
2017 iMac 5K vs late 2015 iMac 5K vs 2013 Mac Pro
2017 iMac 5K vs late 2015 iMac 5K vs 2013 Mac Pro