I'm assuming when you say you bought a Ken Onion, you mean a Kershaw, ZT, or CRKT and not one of his custom knives. I've had 3 of his Kershaws (Blur, Leek, Scallion, all given away) and a ZT0350 (sold). They all came very sharp. Of CRKT's I've handled, none of them came very sharp. Benchmade's I've owned have had very average to below average sharpness. I had to sharpen my 530 almost immediately. My orange 585 mini Barrage came pretty sharp. I had a mini grip and grip and they were pretty bad.
On the other hand, I've never had a problem with Spyderco--I own/have owned many and they all came sharp enough to decapitate someone in one stroke. Lionsteel/dpx has been the same. I've heard mixed reviews on ESEE, but my Izula and 5 came very sharp. ZT0801 is average.
Sometimes I guess with the bigger companies there is so much demand that QC is compromised. Being that Spyderco has factories in Colorado, Japan, Taiwan, and China instead of one or two big factories, they can concentrate more on QC. Just my .02 and experence.