Melbourne is a smaller airport--you can allow just an hour to hour and a half to checkin as opposed to the 2 hours or so at OIA.
Keep in mind though--Melbourne does not have the luggage screeners, yet--all luggage is hand searched. So if you are a big packer--this will slow you down.
Also, all flights connect through Atlanta--there are no direct flights. And our only airline is Delta.
I live in the Melbourne area--and personally love our little quaint airport. Depending on when you sail--the hand screening is going away once they complete their addition and get the screening equipment that OIA has.
Driving distance will be about the same to either airport.
