Depends on the cooker. In a UDS, the heat is coming from the bottom, so fat side down to protect the meat. In an offset, it wouldn't matter, but if it were a brisket in an offset, point closer to heat source every time.
I also agree that fat doesn't melt into the meat, it drops off the meat, so fat side up doesn't help keep it moist. Moisture comes from within the meat as it renders.
Modded Brinkmann Gourmet. Basic UDS. Rescued 22.5" OTS. SJS Mini-WSM. Stubbs. B&B Oak Lump.
Cannondale 2009 F8 (for burning off all the great BBQ)