The top block on the slim fit is monstrous and is meant to sit pretty low on the waist of someone that has enough ass to hold them up. This jean is definitely not for the flat-of-ass. When I tried my actual size on, I was getting a couple of inches of fabric bunched up in my belt in the back, though the jean looked great in the thigh and calf. Upon sizing down one, it fit much better in the top block on the frontside and hips. I can still fit a fist down the backside when wearing them closer to the natural waist, but it doesn't look like a diaper the way true-to-size did on me. The thighs are SuFu tight, though I suppose that will lead to the dramatic fades we all crave--they've already lost indigo in the creases with around a week of wear.
I'd compare the Slim Fit to that of the N&F Weird Guy, with a slightly larger top block and less stretch overall. I am ~172lbs, 6'0", and went with the 31x32. As for the Black Slim Fits, the 32x32 are perfect for me. Hope this helps someone out there.