You can vent interiorly or exteriorly depending on your requirements it's how you vent that's important.
A big box with no flow direction such as a unit pushed up against a wall with an exterior vent and fan tied to the evaporation coils will not be efficient. The air molecules are kind of lazy and if they can they will just hang out in a corner not contributing to your needs. They need direction, give them a nice tunnel to follow and you will have the most efficient flow possible. You can still use a large one piece grill just separate the intake and exhaust. Better yet make a complete enclosed system!
I have various units in use in different applications - Dometic, Waeco, Isotherm, Uline, Engle but I am using the TF 65 in my current build. Why pay Boating prices when you can get trucking prices for the same unit?
Cheers