Flat Nylon strapping is also known as Flat Nylon webbing. It is often used for straps with skin contact as it has a very soft feel. Examples of use are purse straps and bag, camera straps, and leashes. Flat Nylon strapping is almost like the "duct tape" of the webbing family. It's popular for use with heavy duty buckles and high breaking strengths. Nylon is also preferred for high abrasion applications, seeing it has double the abrasion resistance than your common Polypropylene.
Polyester is strongest and most durable webbing listed here. It is great for outdoor or marine use, because it has excellent UV and abrasion resistance. Polyester webbing is also the most customizable because it can be imprinted with just about any color, pattern, text or logo!
Polypropylene webbing is also great for outdoor use! It has excellent UV resistance, and does not absorb water, making it rot and mildew resistant as well.