the only thing that you might want from actual ocean are the critters that may have made the the rock their home,ie peanut worms, feather dusters, barnicals, crabs, mini serpent stars, pods
, but having pure live rock liek this can also bring hitchhickers that are not wanted, ie mantis shrimps, apitisia, spiders.
the use of dry rock allows for a placement of all critters you may actually want on there (with introduction by you as the aquatist) and none of the harmful hitchhichers, but the rock is not as cultured as sea rock. it doesn't have all the little caves and tunnels or pin sized holes where things can live.
i personally would go with 80% dry rock and 20% live rock from another tank or LFS
. you can also add some pods
and critters with a power filter pad from soemone elses system when cycling