I bought the Keystep 37 a couple of months ago after watching LoopOp's YT review. The KS37 features, absent on the KSP, have been invaluable in achieving my goals. The "Chord", "Strum"and "Pattern" arpegiator (no small thing) features, are some of the things that sold me on the KS37 due to the experimental possibilities(see this part of the video
https://www.youtube.com/watch?v=I3iaHNIJFsg&t=1241s).
It never occurred to me that the Keystep Pro wouldn't be an expansion of the Keystep 37 feature set; not in my wildest fevered dreams would I have thought otherwise. I'm glad I found this in time to cancel my Keystep Pro order. I certainly won't be buying two more KS37s; the one will have to suffice. Hopefully Arturia will realize their blunder and release a Keystep Pro that's actually an upgrade to the 37.