The only differences will be the capability of your biological filter and appearance. If you used say 60# LR and 60# base rock, you'll only have half the bio-filtration for a few months (until the base rock becomes live). If you keep your bioload low during this period then you should be fine.
I agree. Basically, I started with all LR because I wanted to be up and running quickly. My second reef started with about 40% LR. The base rock will become colonized fairly quickly. As stated before, just watch the bioload.