The factory cover is usually only available in one model, different colors. If you order a custom cover, you can get one which is thicker, has more slope to the taper, longer/shorter skirts, more/fewer fastener straps, and so forth.
Doc sells a very good cover, and he'll gladly double wrap the cores if you like - small fee.
If the factory cover lasted from 2004 until today, you can count that as above average.