The short answer is no, what either one can do the other can also!
But if you are left handed - you'll like the XSE's ambi-safety. (I actually prefer the stock Colt single sided "minimalist" safety of the 1991 - but I shoot with the thumb locked down, certainly a minority opinion these days.)
The chance of hammer bite is zero with the XSE beavertail. Fleshy hands take note! Although criticized by some as being "not the latest thing", the "downswept" XSE's beavertail excels in a couple of other ways as well. It always depresses fully and if anything, the "downswept" tail makes the gun get tighter in your hand as you fire it. I have guns with both and see no reason to change whatever the gun came with. Both styles work for me.
Grasping groves at the front of the slide. You either like them or you don't. For some it's all about the look.
Guide rod is included on the XSE. I actually find that to be a negative, as it makes the gun more difficult to shoot one handed and field strip. The first thing I did upon getting a new XSE was to replace the guide rod with a standard Colt recoil spring guide and plug. In my opinion it adds nothing but weight to the gun. Others think it helps accuracy, spring life - a recent American Handgunner article says not at all. Take your choice.
Both guns will do you just fine. Some like the more utilitarian looking 1991s, some like more frosting! Your call.
I was in the same position: deciding between a 1991 Commander and an XSE Commander. I really like the utilitarian look of the Blued 1991. I was ready to make my order at a local gun shop when I saw an XSE up for auction at the price of a SS 1991 Commander. Well, I have a XSE Commander coming. My thoughts, if I decide I really like the 1991 better, I can recoop my costs (100%) and get the 1991. Hope I find the XSE to my liking! My plan for the 1991 was.....nothing but lots of shooting. If I did suffer any hammer bite, I would have invested in a Wilson drop-in beavertail. The "tail" on the stock grip safety is long enough that I don't think it should be an issue.
All said, there is nothing prettier than a new deep blue 1911 with nice brown grips. Besides a deep scratch, I have had pretty good luck with my blued guns holding up. I don't "carry" so my pistols (other than my USPSA competition gun) don't get subjected to holster wear. Stainless on the other hand, tends to show fineline scratches very quickly. I still think you should go for the 1991 Commander unless money is not an issue in your decision process.
I have a 1991 Commander, added Trijicon sights and slim grips, and it's a beaut; shoots well as well. I just sold two tupper wares, 9 mm and .45 ACP and ordered an XSE light weight Commander. The 1991 tugs the pants a bit too much.
I haven't seen the XSE, but note in the specs that it has a full length guide rod (why, I don't know. My Gunsite certainly doesn't need one for accuracy.)
My question is whether the guide rod is two piece, or am I going to have to lay in a supply of paper clips to field strip and clean?
I agree with questioning the full length guide rod. I use one in my competition gun, but on a personal protection weapon, I'd rather have the one-hand loading option. I gather you can cycle it fully rearward like a government model. I double check this before I make the final decision to keep it or lose it.
It is a defensive gun, so it should cycle the same was as the 1991 Commander. Why else buy a Commander light weight unless it can be used for defensive purposes. BUT, time will tell; one week from tomorrow when I can pick it up.