DC Direct used to be pretty lousy about sticking to dates until they stopped advance soliciting everything a couple years ago. It makes sense that if you solicit products a few months ahead of release instead of half a year or more, you're less likely to run into problems.
Every company has QC problems to some extent. DC has been really bad lately. Koto's problem is more that the finished product doesn't turn out like the prototype rather than rampant paint defects or things like that. I wouldn't say Sideshow is one of the better companies, as lately it seems like there's always some new controversy brewing (the tailoring on the Batman PF, the upside-down ARC reactor on the Iron Man LSB, etc.).
I'd say Bowen and Gentle Giant seem to have the best track record for putting out high-quality products that aren't plagued by defects or changes between the prototype and final version. And even with GG, the caveat is that they're the absolute worst about shipping things on time. So I guess Bowen wins when it comes to a balance between quality and timeliness.