For me its mainly the angle at which the hair is cut. Maybe my skin is just strange but with DE's and modern crap, I ALWAYS get some sort of irritation and ingrown hairs when the hair starts to grow back. Not so with straights though, its as if the angle the hair is cut is one which does not agitate the skin when the hair starts to grow back.

Theres so much more to straights though. Just knowing that you're shaving with an incredibly sharp, switch blade looking thing that, it big enough, could be used as a weapon, is awesome! Also, there's a lot of history to the art. Shaving with a straight goes back hundreds of years. Not only that, but if you're shaving with a vintage razor, you could be shaving with something that was used during WWI, how amazing is that? Then their's the relaxation aspect to it as RMarsh brought up. I look forward to shaving with a straight, its really exciting for me and very relaxing; my mind isn't wandering or distracted, I'm calmly focused in the present moment. Its also a skill, an art; not every body can do it and it takes practice and precision (and courage as some non-straights guys have pointed out.) Lastly, call me feminine but I'm a sucker for all the accesories that come with straights: collecting different kinds of razors, using European shave creams and moisturizers, and trying different mugs, soaps, and brushes. No clue why the majority of males don't use straights, no razor is better in my opinion.