I would change this line:

I have, on many occasions, considered going from [My Company] to [Competitor] due solely to the pay differential.

You don't want to give the bosses the impression that you are actively thinking about leaving the company. Perhaps say something like:

I know several people that have considered going from [My Company] to [Competitor] due solely to the pay differential.

Other than that it looks good. Not too whiney, but adequately gets the point across that you feel that you are underpaid for what you do.