One of The Great Debates rages on . . .
"Capacity vs. Size" is one of The Great Debates here at TFL. It ranks right up there with "9mm vs. .45" and "1911 vs. Glock."
A buddy of mine has a saying: "If I knew I was goin' to a gunfight, I'd go somewhere else. If I just had to go, I'd bring a rifle. And friends. With rifles." Handguns are a compromise. As compared to a rifle, we (those who carry) give up caliber and capacity in order to have something that we can carry on our person, and with some modicum of comfort. While we can offer you our experiences, it's a decision that you'll have to make on your own in the end.
As for me, I carried a full-sized steel pistol for about the first 3 years that I carried. I've brought two other pistols into the carry rotation since then, so I now have carry guns in small, medium and large. My medium sized carry gun, a G19, gets more hip time than the others, as much as I hate to admit it . . . I carry a spare magazine, so that gets me to 30 rounds of 9mm. (No, I'm not actually expecting to be ambushed by a gang of drug-addled meth-heads. Still, I'd rather have the extra rounds and not need them . . . . ) It's lighter than my full-sized carry pistol and, in some ways, more comfortable. My pocket pistol is great for an early morning run to the store, but more difficult to shoot well. That's the compromise I reached.
I have a little (very little) time on the trigger with the XD line and I liked them. I've shot the XDs in .45, which I found to be a surprisingly soft shooter and an XD (full-sized) in 9mm. It was OK, but I was less fond of it than the XDs. Were it my $, I'd be looking long and hard at that XDm 3.8" compact. In fact, I have seriously considered the XDm .38" compact .45 for a long time. For my life (my activities, wardrobe, etc.), it's in the Goldilocks category, along with my G19 and several others. Not too big, not too small, but just right. Also known as "large enough to shoot well, small enough to conceal comfortably."
I'm sure there's nothing wrong with the XD Mod 2, but I'd prefer to have a little longer barrel and sight radius. It may not make a difference at SD distances, but I like something a little longer for range day. In my experience, the longer barrel won't affect concealability at all, especially if you go with an IWB holster.
As for the XDs, the one I shot was a neat little gun. Yeah, it holds fewer rounds than larger guns, but that's to be expected. I wouldn't mind having one for early morning runs to the store. If you carry a spare mag, you're looking at 7 in the gun + 8 in the backup mag. That's not bad.