Here is the info from the site I linked on the difference in the fabrics. There is also a price difference with each bag depending on what it is made from.
Ripstop: Ripstop is a backed nylon, parachute style fabric, It has a subtle, tone on tone ¼ woven grid pattern that stops rips. Ripstop has a similar look and feel to the nylon used to make windbreaker jackets and tents. Available in 10 bright colors, black and two patterns. Durable, lightweight, easily cleaned and water resistant.
Crinkle Nylon: Backed nylon, this fabric has a canvas look with a woven textural quality giving it a crinkle effect similar to the natural wrinkling of linen. Crinkle nylon, while still casual, is a more sophisticated fashion statement than ripstop nylon. Available in 13 muted, fashion colors. Durable, light weight, water resistant.
Metro Nylon: Similar to crinkle with a higher sheen and slightly heavier construction,
Available in four colors while supplies last.
Microfiber: Microfiber is a polyester fabric that has a very polished and structured appearance. Its light sheen, consistent color and fine weave give it a more sophisticated and formal look than the other fabrications. Available in 8 colors.