I've had the opportunity to shoot both guns. I carry and routinely shoot with an XD Mod.2, which is very similar to the XDs, with about 1/3" extra width. They shoot very similarly, and I found the XDs easy to shoot. It points pretty naturally and is easy to fire quickly. I happen to be a fan of the grip safety, since it does at least render the gun inoperable when you're holstering (properly). I've only shot any XD in 9mm.
I found the Micro 9 comparatively difficult to shoot well, but then it's unfamiliar and I'm not overly familiar with 1911's of any size. It seems easy enough to train to always flick down the safety on the draw, but to me those are always extra steps that could go wrong. It had more of a kick than the XDs (but if you're used to the XDs in 45, then the Micro 9 will probably be a step down in recoil).
Browsing on forums it seems that the Micro 9 is a pretty reliable gun. It certainly looks cool and has some personality. I view the XD series much like M&P and Glock -- uninteresting and unremarkable, but utterly reliable and dependable. I've had zero malfunctions in over 3K rounds through my XD Mod.2 using even cheap, dirty ammo.
The Micro 9 wins on concealability, I'd have to think...they're tiny!
Personally I'd stick with what you have for carry and defense, which is already known to be reliable and easy to shoot. "Boring" is absolutely fine for self defense
If you have the cash, get a real Kimber 1911 for range use or maybe some sort of competitive shooting. Kimber makes some sweet guns ,and their 1911s are like Cadillacs.