I'm not sure if the 'quality level' varied so very much from WotC to 3pp. Well OK, in some cases, yes. But that went both ways.
The OGL still allows (as it has since its release) for total freedom of ideas and execution. WotC cannot match that, of course. No one organisation ever could, even if they had the liberty to take things in certain directions (which Wizards doesn't). And neither can the pitifully small amount of gamblers on the (rather more restrictive) GSL, obviously.
Depends what you're after, basically.