I really like the 1 man. I'm 5'-10" and 165lbs and it's a perfect size. I can sit up in it and get dressed or wait out the weather. I have heard some people complain that the 1 man is too small, but I have not found this true. I put all my clothes, food, etc. in the tent with me. The tent tapers from your head to your feet, being larger at the head. The tent is 42" wide at the head. My sleeping pad is 20" wide. This gives me 11" on each side, that tapers down to my feet of course, that i can put items. I leave my pack and bow out of the tent in a black trash bag. I put my boots and stove in the vestibule are, for easy access in the morning. I think it's a great tent. Having a small footprint dimension gives me more options when looking for a bedding site as well. If you’re planning on being in the tent with all your gear for a considerable amount of time while the weather clears, then maybe look at the UL2. Like you said the weight isn't that different between the two.
I hope this answered your question or at least helped a little.