Both fish are generally a hardy fish, and easy to keep. The chromis are schooling fish so odd number multiples are good - 3 or 5, but not 4.
Chromis are fun to watch as they all swim in a pack and when spooked, will are dart away, and then (5) seconds later they join back up and swim together again.
Clown fish are just like the name... clowns - they will have great personalities, recognition, swimming upside down, etc. Fun to watch and interactive.
Both should do great in a 72 - Also, there are several types of clowns so be sure to research thouroughly on the temperments - there are some that are more aggressive, ie Maroon clowns.