Having been on a shorts quest in the last year, I've found that the fit of the shorts is as important as the construction of the chamois. If the shorts are even a little too big, the chamois will move around, and if they are even a little too small, my parts will be compressed and/or suspended, and I'll move around independently of the chamois. Either way is not good.
I'm on the line between sizes in just about every brand, so it's a real issue. In principle I really like the Castelli Kiss-3 chamois, but when the rides get longer, as far as the "outside" part of the shorts, Medium is too big and Small is too small, and they just get uncomfortable. One of my two most comfortable pairs of shorts right now is the LG Neo Power (in Large, for comparison with Castelli sizing). When I looked at that chamois I didn't think I would like it, but I was willing to give it a try. As it turned out, the shorts fit me so well that the chamois doesn't move under me and I don't move over it, and they're great for all day.
So my advice is to find a brand that fits you very, very well, and pay as much attention to that as to the chamois. If you're one of those lucky ones who isn't on the line between sizes, ignore me.
Speed comes from what you put behind you. - Judi Ketteler