I come from the "old cloth" so to speak. I know Josef from the old days, and I trust him with Printables. Thingiverse was originally Makerbot property, then Stratasys bought Makerbot, and more recently Ultimaker bought Makerbot.
Thingiverse is going to be where all of the stuff originated from, but they don't have any incentives to continue posting there. Printables gives points that can go toward getting their filament, which is really nice, and generally the content there is cleaner and also generally tested beforehand.
Nobody who judges a site based on how many ads there are is worth listening to. They aren't even smart enough to be running an ad-blocker, so why even take their opinion into account anyway?