Let me explain what I mean by "counterpart". The 9mm frame is, ergonomically, historically, mechanically, the standard for handgun design. As such, we're kind of seeing efforts to fit all kinds of ballistics capabilities into the 9mm sized frame. .357 SIG puts fast and light ballistics into that frame. .45GAP puts slow and heavy ballistics into it. Someday, somehow, someone is going to fit .223 ballistics into it (the Saab Bofors round is one attempt..). Fast and light, slow and heavy. That's what I meant by "counterpart".
I can't reach the mag release on a 1911 to my satisfaction. I'll admit that it takes only a little shift of the hand to bring the release under my thumb, but I hate making that shift. I like my guns to fit me better than most. And it isn't the width of any given .45 ACP that's the problem, it's the length. A standard flat mainspring housing doesn't quite cut it.. I haven't tried the super-flat almost non-existent custom mainspring housings. But I'd have to buy a 1911 and modify it just to *try* that.
You notice I said "FACTORY .45". I don't want to drop hundreds of dollars on a gun and then hack it to fit me. I want to buy a gun that works to my satisfaction out of the box. Maybe I'm asking too much in that I want mag release, trigger, and grip to all fit perfectly without requiring any shifting to operate. But if I ask "too much" and the XD45 delivers it, well, isn't that good?