Some say Marshal island rock is the best rock. . it's defined by the aquariast, not by the poster or the pet shop owner or the guy down the street.
Fiji is a good live rock, depending on the rock itself that is, Marshal Island is also good, a little more porous of a rock that equates into more overall space for bacteria to live and it is lighter which means it takes less weight to fill your tank, both are usually a little different in looks and colors of algae on them, but it's you who defines if one is better than another.
Some like different live rock for different reasons, Fiji is usually less expensive than Marshal Island, yet usually has as much life on it as Marshal does.
This is basically the lesson, it's the individual rock that is important, one that has alot of life and you find pleasing to the eye and fits your reef building the best. they are all alive with plants and animals and bacteria, but they all come with different price tags. After all, you can't have what comes on live rock without first buying some for your tank and reoproducing what comes on it.