I've tuned a couple of my neighbor's projects on the Holley. The software is slicker, which you'd expect from a big entity like Holley. I'd certainly run their stuff if I needed all of the supporting hardware. My feeling has been that PxS is an excellent solution for up to about 1000 hp, and the nearly-plug-and-play aspect (and cost) is awesome for milder applications. Beyond that, you're starting to need some ignition behavior that the basic MS3 hardware CAN support, but it's all built into the Holley, and works plug and play with the Holley hardware, so it just makes more sense.
That said, because my RPM requirements are low, if I had the bottom end to support it, I feel pretty certain I could sneak the red truck past 1000 crank hp on the PxS, especially once I get the CNP hardware on it.