Both are good, zooplankton are small shrimp like creatures, usually sps corals feed on them, phytoplankton are small free swimming algae spores which most filter feeders like sponges and featherdusters feed on. Both terms refer to a large group of individual species, ie no such thing as an individual phyto or zooplankton
They are both good additions to a reef tank, although zooplantkton of the correct size and density for sps corals may be harder to find than phyto which can be purchased frozen, live, or grown at home. HTH