I had asked myself the same question when I was looking for a soft top, I went with the twill because of the darker fabric and the reviews that it was quieter. I also like the idea that it was suppose to have a better warranty (for some reason) and I am now considering leaving it on this next winter to see if it holds up.
Black Twill Supertop NX
• Lifetime Limited Warranty – the only soft top you can buy with a warranty this strong.
• New 30-oz. triple-layer Black Twill fabric has superior durability to other fabric used in Jeep soft tops.
• Black Twill fabric as found on high-end sports and luxury cars like Camaro, BMW and Rolls Royce.
• Features a smooth, wrinkle-resistant appearance, and contains no PVC’s.
• More flexible with a softer feel and superior cold-weather performance than sailcloth fabric.
• Industry-leading 40-mil, D.O.T. approved vinyl side and rear windows have 31% tint to help keep interior cooler in warm weather.
• Removable and replaceable windows feature top of the line YKK scoop count zippers for easy removal or installation with extended surface heat-sealing for strength and protection from climate extremes.
• 135 gauge polyester industrial thread use throughout with finished seams for lifelong durability.
• Premium hardware is black powder-coated for corrosion and scratch resistance.
• Features factory-style door surrounds and windshield header assembly, Bestop-exclusive Top Arch Bar, Quick-release Bow Knuckles and adjustable tensioning, just like Supertop NX.
• Bestop-exclusive Flip-back Sunrider sunroof panel for an open air ride is standard on Supertop NX.
http://www.bestop.com/component/products/?view=product&id=138