I use both at the same time, I pre-spray with m/s but still use u/m in the tank. But if I had to choose between one or the other UM would win hands down.
M/S, if nothing else gave me a lot of confidence because they are so idiot proof.
One thing I don't understand is m/s advertising that they don't have optical brightners as if thats a good thing.
How about a m/s WITH brightners, or wouldn't that work?