Springfield claims 33% lighter spring weight for easier slide racking. It is a deliberate design choice and it's noticeable when racking, although I don't find most guns hard to rack, I could see it being valuable to someone with less hand strength, arthritis or the like.
I had an XD Mod.2 3" for about a year and really liked it. It's quite small for what it is. Honestly, the XD-E isn't *that* much smaller. The thinner profile is noticeable, but the overall length is slightly greater and the XD-E is quite tall. It's also very heavy. Between the two, I'd suck up the slightly greater weight and width and get the Mod.2 for the extra capacity.
The XD-S is a bit smaller than the XD-E and is striker fired like the Mod.2. If you want a smaller gun, I'd opt for the XD-S since it has a shorter grip length and is more concealable than the XD-E.
The E's trigger is decent -- longer than I'd like, and the DA pull is so-so, but the SA pull was pretty good, although with a long-ish reset. The Mod.2 trigger is about as bland as it gets, kinda mushy, not terribly crisp, but more than sufficient for a defensive pistol. I wouldn't say any of the Springfields are especially great in the trigger department.