I shot IDPA last week with a 40 year old HK P9S. DA/SA, heel release mag, 4 inch barrel. I was no superman, but I shot well enough on several stages to get a few admiring grunts from the regulars. I don't find the DA to SA transition to be a big deal, and my mag changes were no slower than slingshotters'. I also shot part of one stage single handed.
I came across this forum and was amazed to find people here who are actual proponents of DA/SA and LEM triggers, rather than Glocks with 3.5 connectors and 1911s.
I also recall years ago when IDPA nationals were won with P226s and Beretta 92s.
For this type of "practical" shooting, how much does the platform matter? If some of those terrible grouping M&P pistols are reasonable choices, just how much extra time or dropped points should someone shooting a 92FS or a 5904 expect over those shooting Glock 34s or PPQs? If you can control a DA trigger, is there really that much difference with any 9mm pistol at those ranges?
Reading the recent thread about the HK P30 woes shooting one handed made me think that shooters emphasize many aspects of gun design, but in the end the gun didn't work because the grip didn't index well, making all that other stuff irrelevant. I'd kind of like to think someone with good DA trigger control could buy a $400 Bersa and shoot 99% as well as with whatever wonderplastic they normally use.