I believe neoprene is supposed to be one of the better materials. My EMPI boots are neoprene but after 2 years I'm starting to notice minor micro cracks developing on the creases. I've also bought Napa branded CV boots and although I haven't put them in service yet, the materials appear to be much thicker and sturdier than the EMPI boots plus they have a lifetime warranty.
I've also notice all CV boot kits only give you about 100g of grease which hardly seems enough. On my 4Runner the OEM specified amount is about 250 - 300g. Some OEM joints also use a different grease on the inner vs outer joint so maybe using the same grease might not be optimal?