Confining the comparison to AO, I would overall lean towards Kershaw. The two AO knives that appeal to me most are the Mini Cyclone, and the HK Blitz (made by Benchmade). I don't have the money to get either anytime soon, but it would be a tough choice for me between the profile (particularly when closed) and G10 of the Blitz, and the on/off feature of the Mini Cyclone. To me, that on/off switch is a huge factor in favor of Kershaw.
Just for knives in general, though, I tend to prefer the designs that Benchmade produces. Also, if you're not dead-set on AO, then I'd actually recommend a BM Axis lock knife of some sort (the Presidio may be my favorite, but the Grip line, Osbornes and HK Axis locks). The great thing about the Axis lock is that it can open AND close as fast as an AO knife (particularly the 94x series).
Just my $0.02.