The OU as an organization is driven by profits and reputation. I am looking for hechsherim that are driven by yiras shomayim or at least someone perceived as one is telling you it's OK.
Professionalism and expertise are also crucial. But secondary.
In today's complex and interdependent world of food production, professionalism and expertise are not secondary, but are equally necessary. With the best intentions and yiras shomayim, one might simply not have a clue as to where problems could occur.
That is why Eida Chareidis and Rav Landa of Bnei Brak are considered to be be at a different level than all others, due to the combination of these ingredients. I find it as no coincidence, that both of these (while Kashrus is a significant source of income) have served and will serve even without the Kashrus organization, something that can't be said about many (if not most) other (even "Chareidy") Hechsherim.
That being said, I once had a conversation with my nephew, who proudly announced that he will only eat Badatz (Eida Chareidis) and Landa, and couldn't understand why his grandfather (my FIL) had such disdain for such a statement. I explained to him that while no one refutes the fact that those two Kashrus organizations hold the highest (or strictest) standards, one shouldn't think for a second that if he decides to rely only on those two, he is in any way holier than one who would accept more lenient Hechsherim. If you decide that you want to be machmir for yourself, תבוא עליך ברכה, but once you make it public, it smells of "holier than thou" וכו׳ וד״ל.