Have a Ruger MK IV 22/45 Lite but find myself looking for another 22 pistol. Considering the PPQ M2 or possibly Ruger SR22.

Can't seem to find any comparisons of the PPQ vs the MK IV, only to the SR22. Those seem mixed in recommendation. Is either going to be a disappointment from the MK IV? I have and like my PPQ M2 9mm so thought the PPQ 22 would be a decent choice.

ETA - Only real requirement for the new pistol is that it can support a suppressor.

I am very pleased with my Ruger SR22 pistol.

My SR 22  and Dead Air Mask are the two most fun things I shoot, lately.

I've only shot the SR22 but since you have the Walther PPQ 9 the 22 LR PPQ M2 makes sense.  My Brother in Law has the S&W M&P 22 LR and I like it a little better than the smaller SR22.   I'm a Glock Guy and I really like my Advantage Arms 22 LR conversions which have threaded barrels available.  Not the cheapest route but I've bought Glock frames which I've dedicated to my AA kits.   I really don't think you can go wrong with any of them.

My first pistol many years ago was a 5 1/2" Bull Barrel Ruger Mark I.  I like shooting the AA conversion Glocks better because I use the AA/Glock since the platform matches my CCW Glock pistols.  I shoot Glock pistols the most but it is the trigger time that makes the biggest difference in shooting a pistol well.  Has worked well for me to practice with the same platform with rimfire whether AR-15 or Glock.

Have the PPQ M2 .22 and the Ruger SR .22.  I enjoy the PPQ better because it is full size.  The Ruger is too small for my hands.  Both have been 100% reliable with my Gemtech Outback.

I'll see if my local range with rentals has either or both to try out.

I probably shoot mine more than any other gun.

The wife got a PPQ .22 after shooting one at the range a few times.  

It feels like a 9mm with a .22lr conversion kit; it's the best full sized .22lr short of a Kadet IMHO.  

And you get the 12 round magazines too.