...and results were a bit surprising.
At least for the two examples I happened to pick up, both trigger pull quality and reset quality favored the Shield. I had remembered both a crisper trigger and shorter reset when I first met an XDS, but not so on this one. (I may now make it a point to try out every one I see, just to have a sense of how variable each one can be.)
The Shield's trigger is indeed the partial-cocking striker-fire variety, and I was impressed. At least on this example, it was superb--it reminded me very much of the impression I'd got the first time I saw an XDS. :-)
Other variables went back and forth. The trigger guard on the XDS is better for gloves than the Shield's... The Shield actually felt slightly slimmer in the grip than the XDS, but recall that the Shield's magazines have a slight stagger that make them noticeably thicker than the XDS' true single-column tubes... There's the whole 6+1 .40 versus 5+1 .45 comparison... The Shield has the potential for a manual safety, but without a 1911-esque thumb extension, I might actually prefer the sans-lever model... The XDS is very slightly smaller in height when both guns use their short magazines, but it's very much taller when the long magazines are used...
Really, it's kind of a wash, with all things considered.
And if I'm honest, I can also compare both the Springfield and the Smith to my Kahr CW40, which is 6+1 .40, 0.94" wide, 4.6" tall and 6.3" long (read: effectively the same), and realize that its only real disadvantage is the revolver-length reset, which frankly only matters to me because of the (potential) glove problem. The Kahr's trigger pull quality is better than either of the other pistols, it's lighter, and its grip frame is one length, rather than "extensible" by a longer magazine that also tries to replace grip space. The grip is also large enough to get the whole hand on comfortably.
All duly noted. I suspect that one would be well-served by any of these three choices.
I admit I'm still intrigued by the idea of the XDS 4 playing the role of LW Commander, with the ability to suddenly become a subcompact in grip profile, as a newbie's first and most-flexible piece. .45ACP is pretty forgiving for a general purpose cartridge--moreso than .40--and in the end that might what sways a recommendation.
Looking forward to my first range experience with either of these newer designs. :-)