Whatever you use, I've found that buffing the tires after letting the product sit is really a good way to keep them clean longer. This way the excess product is removed so it won't attract dust/dirt. In the case of 303 (and probably others), it is actually recommended as this buffing "sets" the product, increasing the durability (303 website has more info on their product and buffing).
I've used Endurance, 303, Vinylex, #40, NXT Protectant, and others, and always buff them after the product set for some time. It also gets rid of the "plasticky" shine with high gloss products, helping to give a satin, black look. Actually, I switch between the above products about every wash just for the feeling of doing something different. Each one has it's own subtle difference in appearance.
Endurance and NXT are both too shiny for my tastes without buffing. But after buffing, they look really good, even if a little shinier than 303, #40, and vinylex.
The NXT has actually impressed me with its appearance. It looks oily when applied, but after buffing it has a dry, satin, BLACK appearance. It's durability is better than the others (which have worn off after several rains), with the exception of Endurance. But I don't even know the limits of those two as they've never worn off before I'm doing them again.
Just my experiences.
Dave