Pre algebra gives you an introduction into algebra 1. It covers less material than algebra 1 so its a little slower paced. On the one hand, pre algebra lets you be better prepared for algebra 1 so you could be more likely to get better grades. On the other hand, pre algebra will take up an entire year and if you took algebra 1 you could take more advanced classes later on, and look better to college recruiters.
My vote, if you're being given the option that means they have confidence in you, so if you are confident you are willing to learn I'd shoot for skipping pre algebra.