Definitely go with the internal overflows. Much cleaner set up and you drastically reduce the chances of developing leaks.
Also...Make sure that you fill up your tank with regular water and test for leaks before adding your saltwater mixture. My lfs had a couple of bigger tanks, both All-Glass and Oceanic, develop small leaks that had to be simply fixed with silicon. Shame to waste all that salt and mixing time to be forced to drain it all.