Seven High said:
They are both the same frame. They are interchangeable.
I'm pretty sure they are NOT the same frame. They are similar.
Compare photos, if you don't have access to the guns, and you'll see that the decocker guns are a bit wider through the frame, above the trigger (the yellow line/arrow in the photo). It's like there's an extra layer of metal. I don't think it is an extra layer of metal, but the gun is WIDER in that area.
The newer PCR is, I think, different than the older PCRs, as well, but not in ways that are likely to affect holster fit... and the new PCR has the extended beavertail (not an issue with regard to holsters). It also has, I think, a reversible mag release, while the Compact doesn't. Any and all of these things can affect how the gun fits in a holster.
Folks who have both say there is a subtle difference, and some of it may simply be the decocker, which sticks out farther than the safety. It may be that the upper part of the frame is WIDER on the PCR. (I've never measured them to compare.)
If you have a holster that's a bit too tight, you can heat up a kydex holster with a heat gun (like are used to remove tile -- Harbor Freight has them for under $10) and then insert the gun, and it'll take a new shape. Be careful, however, as too much heat will MELT the holster.