Two completely different playgrounds.
If one already has a PS4 and wants access to the next gen of Nintendo games, the choice is obvious.
If the reason for replacing the PS4 with a PS4P is to justify using it with a 4K display, I'm not sure I consider it a bargain to knock $100 off the MSRP by selling the PS4 considering they play the same games.
Originally, I was under the impression that the PS4P was the stealthy way of SCE re-releasing a console that would actually have the processing power to properly run PSVR without compromising performance (calling the pair Neo and Morpheus while in development was a hint). Unless you have or have immediate plans to buy PSVR, the PS4P becomes a harder sell if the primary reason is "because I just bought a 4K display."







