Well, each builder was given one shot at this, and each had their own goals. So that is 3 enclosures out of quite a large number of options. (This $400 build wasn't planned, just IMO it needed to be done and Chris agreed).
Crash already stated why he didn't use the FT03. And really, although rather large, most folks loved his Prodigy build.
On the low end, the pictured SG05 (and V3+) are ones I bought myself, nothing to do with the SBM. Yes, personally that is exactly what I wanted to use for the $650 PC, along with a GTX 660 and 8GB if possible. Going in, that was my expectation for the Gaming PC. However, it was $115, robbing $25 more of this budget. I had to admit the $40 120 Elite with Tahiti LE grabbed far more sheer bang for the buck. More than ever this SBM I faced a conflict of interest between what would perform the best and what could best find a place in my own home.