I choose downmat/synamat over thermarest because they are warmer, they fold smaller for the thickness I need (ignoring the neoair as too cold), they have a chair kit that you can use to sit up in bed, which I find really useful for back problems and also for reading. They have always replaced promptly when I have had problems.
In about 16 years of fairly heavy and not careful use (Nye jumps all over them) I had one of the old style valves fail, one puncture (clarion's flimsy ultra light), and 2 baffle failures, one of which is also the the UL. They have replaced everthing with no quibble, even the 12 or so year old valve failure. They repaired the puncture. So whilst not a perfect record, pretty good for 16 years. We currently have 3 in service plus the UL which is waiting to be sent for repair.