I think it's choice "D. All of the above."
I think some folks really are more trigger-sensitive than others, and some are in-turn more picky than others. I personally don't see anything wrong there: it's just personal tastes.
Other times, there truly may be deficiencies with that particular weapon: production tolerances are what they are, and not all examples of one make/model are built precisely the same.
Personally, I am not the most trigger-sensitive shooter: I need to really, really concentrate on feeling the trigger path in order to pick out sometimes even quite glaring characteristics that others can pick up/out almost instantly (see picture below), but I'm definitely also far from the most inexperienced Greenhorn.
So, with that in-mind, I will tell you that I spent over an hour at one LGS a few years ago, trying to pick out a Kel-Tec PMR30 that combined both a reasonable trigger path with a slide that didn't take excessive force to actuate
(
https://www.xdtalk.com/threads/xd-trigger-differances.369529/#post-6340489 - the pistol was for my then 13 year-old daughter, offering her a stepping-stone between .22LR and centerfire). I kid you not, the clerk and I opened a dozen boxes (they had over 40 in-stock, but I was only interested in either black or gray, so that narrowed our task) and hand-cycled/dry-fired each one, and we both marveled at just how different each gun was from the other: the consistency was just not there.
Overall, I tend to need to work extra to properly characterize triggers:
Below is a picture of me and a classmate from a two-day handgun class a few years ago. This live-fire exercise had us shooting into the berm, bracing the handgun on our abdomen so that we could focus
absolutely -both by feel as well as visually- on the entirety of the trigger path:
That was March of 2017, so that was probably 12,000 to 15,000 rounds on that gun, at that point?
In an effort towards more consistency, I've put in Springer Precision kits in all four of my XDms. Even so, the oldest of the four still has an ever so slightly different path than the others.
Another example that illustrates my point is when a friend of mine -a frequent-flier at local training classes- brought his then-new P320 to the class. Until that class, he'd shot only his 4.5-inch XDm9, so he was having some "teething" issues with trigger control that manifested on the higher-demand shots. Our instructor took the gun and tried a few test-shots with it, and remarked "that's interesting," when I stopped him and asked him not to tell me what he thought, and in-turn took the gun for my own assessment: it took me several shots - including clearing the gun out for dry-fire - before I was ready to offer my thoughts, to see if they matched with that of the instructor's.
With the ARs, as back-to-back examples, I've got one with a Geissele SSA-E, one with a SSA, and one with a G2S. For my level of trigger-(in)sensitivity, I can't really tell the difference between the SSA versus the G2S without physically looking at the triggers. That said, blind taste test by just holding the lowers, I'll do the challenge every time and pick out the SSA-E. My daughter's Larue MBT-2S's shoe physically feels different versus the Geissele triggers, so that makes the blind taste test a no-go, but even so, I am quite certain that I could tell the difference between it versus the SSA/G2S.
I think what's most stand-out to me the difference between a factory "USGI" single-stage AR trigger versus a good aftermarket like the ALG ACT, BCM PNT, Sionics EMT, SOLGW LFT, etc. It's a very appreciable difference, even for complete novices to grasp. Then you drop in a Wilson TTU into the mix, and whoa.....
