1st two why? A pistol is a back up gun. if you can hit centre mass at 20m you're laughing. if that's your criteria H&K MK23 is the best. No blow back to throw of your aim, It will out range AEGs and its function is less harsh than a GBB.
If you want a GBB they are all pretty much the same performance wise. on 144a gas with 0.25g BBs you can get consistent hits out to 35m to 40m.
the newer models HK45, FNX 45, M541, m9, 4th gen Glock all have newer design Blow back unit which is more efficient and nicer finishes.
I personally Like the HK45 but in the end all of them will pretty much be better than any other brand of GBB. Yes they can run on high powered gas and it will shorten their life span. they are designed to run on 144a and that's all they need.