An internally geared hub is slightly less efficient than a derailler system, on the order of 1-3%. A filthy chain on a derailler based bike can add far more inefficiency. The main advantages of an internally geared hub are shifting at stops (which is a godsend if you ever have an emergency stop with 40lbs of groceries), and the ease of protecting the chain from the elements (which is primarily of interest in a wet or snowy climate). The latter advantage probably isn't in AZ.

If you're not looking to use the bike as a car and still want the clean look, I suspect you might be better off with a singlespeed or fixed gear bike, geared so you can work on your spin. That eliminates the inefficiency of a shifting system, lightens up the bike, and should net you helpful gains for racing. There are a fair number of road focused bikes along those lines that should work well for you.

If you're the sort of rider who really focuses on a consistent cadence, IGH and singlespeed are unlikely to be fun for you tho... both styles of bikes have a *lot* of cadence variation.