Well....
I'd say, try to look out for stuff with innovative designs or at least, stuff that tries to go a step in a better/different direction.
I'm not an electronics guy but when I've heard, played, seen, read up on the 1 millionth tubescreamer clone... or some other drive that uses that JRC op-amp... I kind of expect similar results in sound & feel.
Maybe that is what rocks your boat but I've heard stuff thats seemingly tubescreamer like but yet, offers more than the old 3-knobs and a footswitch config - look at Edder's od pedal. I really like the pre-gain control, which isn't commonplace.
I think going after the design is more... rewarding than going after a different brand since a brand doesn't necessarily mean innovation... unless its uh... Subdecay? Zvex? I dunno...
Again, I'm not a techie, and I usually ask the tech ppl what they think of this or that, or even speak to the builders, or query the more "serious" players what they think of it... in order to like, not spend on something that's just a re-hashed pedal.