Both are great guns. The PPQ I think would be a step up for certain. Even with the Apex kit I still prefer the PPQ over my decked out M&P Pro. The SIG 320 would be at least the equal of the PPQ. I have not shot the X5 but the regular 320 is no slouch and is going to have full support for at least the next 30 years due the US Army having chosen the design for their duty pistol.
I should add I had them out this afternoon and from a practical sense I shot the Match, the PPQ M2 5" and my M&P Pro equally well. There really is no daylight between any of them for use in IDPA IMHO. I like the grip on the M&P better than the PPQ but they may be because I have shot it more. At 10 yards they all shot to an inch or less at 10 yards freestyle with about a one second cadence. Anyone of the guns, be it the M&P Pro, PPQ Match/M2 5",the 320 or 320 X5 will serve any shooter well. Pick the one you like and shoot the heck out of it.
Take Care
Bob