Some guys are much better and competent pilots at 300hrs then some guys at 3000. Its not the amount of hrs its the quality and the quality of the person. If you think you can make it at the regionals at 400hrs or whatever then go for it. I agree that instructing is good experiance but lots of people never went that route and many flight instructors get lazy even if they have tons of hrs. I think with what those regionals pay 300hrs all they should require.

Anyway, just be sure you can make it through training or else your screwed.