I actually prefer the 147 grain HST in short barrels over the Gold Dot 124 +P, I carry the HST in my SIG P938.
But given the choice between 9x19mm and .45 Auto...I'll take the .45 every time. I just love shooting it.
Of course, I still think you should Get Both(TM). I want a USP9 Expert too.
Just not as much as my Elite.