I am currently waiting for my Saltwater tank to be ready for fish. Should I get coral or crabs before then?
The tank will be ready June 12th
Get coral. You don't want to get crabs...believe me.
I think that both choices are good although personally, I would go for the crabs. This is because they tend to adapt very quickly and their maintenance is manageable. See http://www.aquacon.com/crabs.html.
Get coral first, so it will be a new environment for the crabs when they get in the tank.