Crobat, because Pidgeot fails in absolutley every way. It has horrible stats in all categories, and it's movepool is so dire that Hyper Beam is standard on it.
Crobat, on the other hand, has excellent speed and a great movepool which allow for a great hit-and-run strategy. Unfortunatly, it's much harder to train than Pidgeot. I trained both on FR and raising Golbat's happiness took alot of effort, plus Golbat's bad stats prior to evolution made battling and training with it stressful. I don't like the looks of it either; to meh, it's just a toxic-colored blob with nasty looking teeth, spikey little ears, and a set of cheesy wings.