Here is my $0.02 on the Sitka Ascent, KUIU Attack, and Sitka Mountain Pants...
Sitka Ascents: Great early season pants. Lightweight fabric, has more bells and whistles than KUIU (silicon strip on waistline, snaps to aid in rolling pants, etc), very comfortable. This tends to be my goto early season pant. Slightly cooler than KUIU Attack pants.
KUIU Attack (Original Vias w/o hip vents): Slightly heavier fabric than Sitka Ascent. Less 'bells and whistles' than Sitka, but very comfortable. Basic pant that reminds me of the original Sitka Mountain Pants (2005/06 timeframe). Very lightweight pant and comfortable pants. Very wide range of use, from early season to late season.
Sitka Mountain Pants: Fabric seems a little heavier than KUIU Attack pants; more bells and whistles, thus heavier weight than KUIU (don't remember the exact weights however), Optifade camo pattern seems lighter than the Ascents, I personally really like the kneepads. I mainly wear these pants during later season hunts. I don't like the built in belt and wish the back 'belt loop' was slightly larger to accommodate a regular belt. Tempted to sell them and buy the Timberlines even though at first I didn't think the waterproof seat and knees would be necessary, but since I mainly wear my Mountain pants later in the season, I can see the benefits of the Timberlines, although I don't think I'd like the zippered front pockets on the Timberlines.
All three pair of pants tend to snag in clingy type brush (catclaw and the like). All three dry quickly and are very comfortable to wear. KUIU Attack are no frills, comfortable pants and I like the longer inseam. KUIU are probably my favorite pant. I normally wear a 33x32 pair of jeans and have 34x34 Ascents, 34" KUIU pants (unhemmed), and 34"x32" mountain pants. All fit well and I prefer slightly longer pants to keep my boots covered while sitting, as long as they don't drag on the ground at the heel. None of these pants do while wearing boots.
Ron