I've got one of each.
The Stillwater is a nice traditional looking kilt, but not tailored. The length and the taper from waist to hips might not fit just right depending on your measurements. In my case, I need to wear the stillwater a little high because I really need a 22” length.
The USA, on the other hand, fits perfect. It sits right on my waist and is just the right length. I wish it had buckles instead of velcro, but the attention to detail is flawless. The apron is cut so the pattern is perfectly symmetrical. It is cut wider at the bottom so it doesn’t curl out (something the stillwater does). The pleats line up perfectly.
Of course, the stillwater is comfy and has more fabric. And, of course, the Velcro on the USA makes it easier to put on and off.
I like them both. Maybe you should just get one of each and tell us which one you like best.