Not sure about the Pro Urbans, but the older styles (pre-Stryker) had a fairly low rise. I have a pair of the P-40's (?) and in a long inseam (36"), and the rise is, well, too short for taller guys. Basically, the zipper doesn't come down far enough to make it comfortable whipping old roger out for a whiz; you have to fully unbutton (PITA). All the newer designs though have a taller rise and are no issue. I have several pairs of Crye Gen 3's and four pairs of UF Pros (based on work assignments, I wear these at work as well) and the UF Pros are more comfortable and better designed IMHO. Nothing wrong quality wise with the Gen 3 Cryes, but the design is older. The latest UF Pro (Stryker X) has done away with the exposed calf pocket (it's built inside the pant leg now) and has a better adjustment for the lower leg (rather than just velcro tabs like the Crye and Vertx pants). Not a big deal (the leg adjustment) for most, but when you've got some heavier items stored there, it's a major improvement. UF Pro has put a lot of thought in the design of the legs of their pants (I really like the boot hooks up front, and the zippered back for controlling how they stack on the boot; less shit to get hung up on pointy corners of vehicles and ladder wells of vessels).
As to why Crye is always out of stock...I ain't buying it. They just don't give a shit about anything other than the military sales (hence why their CS is a joke). Shrug...their choice. Like I said, I've taken my money else where. Kitanica, Vertx and UF Pro, depending on how harsh/rugged (Kitanica) they need to be or how comfortable they need to be (UF Pro). The Vertx are a nice middle of the road between comfort and price (they have no stretch panels, but have similar pocket lay outs).
BTW, both the UF Pro and the Vertx are lean cuts. i.e. They ain't made for the couch potato shaped person. Kitanica's are a bit more roomy (in the thigh). All of them are...supportive...in the groin (which is intended).
Like others have said, currently, UF Pro get's my nod for the best pants out there (based on price, layout/design and comfort). Kitanica's get the vigorous nod for toughness (brick shithouse tough). And the Vertx for just all around price and comfort, with some decent durability.