Not quite as simple as that. From the sucker's point-of-view, if I like a dick because of its size and "looks", I don't care at all if the guy has abs of steel or if the face could land him a modeling contract. What's important to me are hygiene and a friendly attitude. The "notches on the bedpost" criterion, if valid at all, applies equally to the guys who are the objects of desire. Many, many times the guy with the big dick will pick the "hot" guy over all others for exactly the same reason, just with different filters: he can simply get the younger, hotter, hairier, smoother, shorter, taller, whatever guy because of his big dick, and the mouth, even under these picky circumstances, is nothing other than "just a mouth". If the guy (or girl) is "hot", the quality of the blowjob doesn't really seem to matter. Just take a look at professional porn: most of the oral scenes (both straight and gay) are terrible, the big cocks (on hot or not so hot guys... Ron Jeremy, anyone?) are paired with attractive (in the eye of the beholder) guys or girls, and eventually all leads to fucking anyway, but that's another story.
So, if attraction to the person (or the ideal fantasy sex partner) trumps over "the mouth", then the guy with the big dick is not really interested in a good blowjob but is instead looking to score just another "notch on the bedpost".