UCP works ok if you get it dirty using the dirt where you are going to be operating but over all it was made to blend in with Urban/ and NIR
I think Multicam would be the best choice in most situations but would fail in the following Urban/Pure desert/ Snow/Gray woodland/ tropical green
I think US forces should have ACU-Marpat-Multicam-l in digital form -Snow digital to choose from depending on where they are going to be stationed at.
here is a test I did a while back
ok so I did another test to see why ACU was chosen and if it does work better dirty or clean and here is what I found
In urban it works better clean, and in woodland you want to rub the local dirt into it. Check out the picture below I rubbed a little dirt in on the sleeve and it changed colors matching the local terrain perfect
And here is a picture comparing Dirty ACU to Multicam
here is a picture of clean ACU dirty ACU and Multicam
Marpat on left ACU in middle Multicam on the right
Marpat was the top performer but ACU does work good enough in desert
here is an urban test I did