NOTE: I helped with the design of the 2013 Alios (cut and fit/material), so keep that in mind.
The only downside to the mountain pant (for me) was the fit. I have large thighs and calves, so I had to buy XL and cut 3 inches out of the waist line of the mountain pants. Doing this helped me get away from the skinny pant look.
The Alios will have more pockets than the Mountain, but depending on the person, that can be good or bad.
Both have knee pad options, but the ALios has an adjustable strap to help hold the knee pad in place.
The material between the two is basically the same and so is the craftsmanship, so I see no advantage to either on that.
I don't think either is bad, so if you like the Highlander camo and pockets, do with the Alios, but if you're wanting less pockets and Opti, get the mountain.
Hope this helps.