Ok, so I've got another technical question and decided to make a separate post in case there are others looking for similar info that's not related to my Overlapping vs Wasted space post. I'm currently working on a Castle environment that I'm going to be putting together in UDK. I'm using modular pieces with some tiling…
I'd just join them together - it's going to be a nuisance placing the two objects together like that every time you want to place a wall. Udk counts each section as a drawcall. A section is split by material ID then split again at the object level. So your wall is going to be two sections no matter what you do.