Pulleys allow to spread the tension on the leading edge bridle attachment points at various angles of attack, so all parts of the bridle are pretty much equally tensioned on a range of AOA, and across the windrange. So in theory, the intended profile and bar pressure is maintained on a wider range of conditions than a fixed bridle which is optimized and locked around a given set of AOA and windspeed.
But of course pulley and bridle are only one set of parameters in the design of a kite, how well the profile is locked in place at the various windspeeds and AOA will be critical for that. From what I understand, the center of lift on a deep profile tends to shift backwards as the windspeed increases whereas a thinner profile won't do that as much, as the drag component isn't increasing as much. So designing a kite with a thick profile without pullies might be a harder task than a thin profiled one. Or there would be substantial changes in the bar pressure.
But in practical usage, when you reach the top of the windrange or when depowered more, is it actually beneficial to keep an optimal profile? If your profile starts fluttering and with that killing some of the lift, this can help keeping the things slow and manageable, and be perceived as an advantage. Similarly, an increased bar pressure is not necessarily a bad thing for some segments of the market. So it's just one parameter in the design, along with profile distortion, and that's just for flying in straight line. Because how a kite turns matters a lot for riders, this is also to be combined with twist, and all... Complex shit, compromises everywhere!
Now from experience, I never experienced pulley failure, I've had to replace worn bridles on a kite that had obscene amounts of hours of use, but that's totally expected, took 1 hour and $20. Main factor for me is to have short bridles that cannot get anywhere to wrapping around the wingtip cause this is bad, really bad! And for a while fixed bridles where typically longer than pulleyed bridles. (There were also long pulleyed ones, by the way
...). What I liked the most on my pulleyed kites, (GK Trix, short bridle, 2 pulleys per side), was the retained responsive steering wherever in the window, even with barely tensioned lines/ drifting. What I didn't like that much was the way the kite rocks back and forth on its pulleys when lit on choppy/waves conditions, with pulleys doing their job at every change in tension, and with resulting feedback in the bar/harness. Typically a sign that it's time for a smaller one though.
On my fixed bridle Enduros, despite a big wind range, I find that when maxed out, the profile flaps a fair bit, which is not necessarily a bad thing in itself, and there's also a tendency to backstall when too low in the window heading towards it... On the other hand, that's why it can backwards relaunch too... so not necessarily a bad thing either within its design brief.
