The current production XSE's are awesome 1911's... as were the older XS models. I'm perfectly happy with either, though the new XSE's are much easier to come by. The only thing I would (and did) change about the new XSE is the grip safety... I don't like the duckbill safety they are currently shipping with... but that is easily corrected with a Wilson drop-in grip safety.
Feature-wise, the new XSE and the old XS are very similar.... off the top of my head I think the XS only differs in that they had an upswept beavertail grip safety.
If I were you and you have a hard time finding an XS... just consider that the new production Colts are of superb quality... just buy a new XSE in stainless steel or blued carbon steel, drop in a Wilson grip safety and you have a superb tactical-style 1911... the new XSE comes with dovetailed Novak style sights, extended ambi-thumb safety, high cut front strap, lowered & flared ejection port, and the only MIM parts on a new Colt are the sear, disconnector and magazine catch. Replace those three parts with top-shelf goods for about $70 and you have a completely MIM-free 1911 made entirely in the good old USA by the original maker of the 1911.... you can't go wrong with that. It's the GOOD stuff!
In case you noticed... being a true 1911 freak... I just had to swap out some parts... on a contemporary-styled/tactical 1911 I prefer a short GI-style, single-sided thumb safety, arched MSH, solid or two-hole trigger, upswept grip safety, and GI-short recoil spring guide rod.... so I made those mods to my XSE... but none were made out of necessity, all were made out of personal preference. The gun was and is drop-dead reliable with a wide variety of ammo types and magazine brands... as I expect of current production Colts. (I have purchased over twenty new Colt 1911's in the last few years.)
I'd say go forth and buy yourself a new XSE!