Why discuss the materials of the different models when you can just look them up! There are excellent descriptions and pictures of the different models at
www.dui-online.com .
TLS-350 is trilam, nylon-butyl-nylon
CLX-450 is trilam, nylon-butyl-cordura
FLX-50/50 is trilam top/crushed neoprene bottom
The CLX-450 is a little heavier and stiffer than the TLS-350, and more abrasion resistant--generally the choice of cave and wreck divers. Dries almost as fast as the TLS-350.
The TLS-350 is light-weight, dries fast, and packs small--great for air travel. And while not as abrasion resistant as the CLX-450, it is darn tough.
I ordered mine near-blind off the sizing chart; I did first phone DUI and have one of their service people talk me through my physical characteristics and fit preference as it relates to their sizing. I like my fit a little loose, so I can add thick long johns under the undergarments and still have good movement. I ordered the Large suit and undergarments, in spite of their tech suggesting the Medium, and I am perfectly pleased with it. I am 5' 10", 175 lbs., 34/32 pants, 42 reg coat, 16-1/2 32/33 shirt size. For the record, I went with the CLX-450. If I weren't a cave diver, I would definitely have gone for the TLS-350.
Hope some of this is helpful,
theskull