If you have to choose between these two, take Crandon Park.
Even though Miami Beach GC is a re-do of the old Bayshore GC it is not all that great...at least from the view on the road.
Crandon Park has some interesting holes, great views, and the wind can make for a very interesting round.
I'm sure others will chime in here that you should drive NORTH towards the Ft. Lauderdale and/or Palm Beach areas...and if you have the time (1+ hours from wherever you are in Miami, give or take) I might do the same. There are some MUCH better places to play a bit farther North, but it all depends on where in Miami you will be and what kind of time you have allotted.