I have a pair of MUSA pants, and I like the aforementioned Wrangler ATG pants better, mostly due to fit: the MUSA pants are quite baggy, and the newer versions are shorter and even baggier. Not great for tall and skinny me. The ATG pants fit much better for 32x34 me.
The front pockets on the MUSA pants are better, super deep so my phone is super secure but still easy to get to. The Wrangler's pockets are a bit tighter.
The Wrangler pants look more normal--I could pack them as travel pants, for instance. The Riv pants looks... less ordinary.