Prop might be easier. 

/shrug
I dunno, I'm in new territory with the Millenium Dog LE. I've never rigged nuthin' for it. Using the hard-surface armor as props might be easier, but I might try to do something different and give those parts a different bone/group structure, turn off bending and such, and combine them with the rest of it, just to learn a bit about how to accomplish that. So, it'd all, just about, be one conforming item with three to seven additional bones, for the hard-surface groups, so they can be tweaked. (That's probably overkill, though... You're probably right - It'd be more functional an easier to use with certain parts as props. :) But, then I wouldn't learn anything new. :D )