Have you ever seen any labels on the bottle/can from any brands of wax that mention DO NOT USE ON WHITE CARS? Well....I haven't....and I've never heard such a thing.

Maybe what the article meant to say is you couldn't get that deep carnauba-look on a white coloured car when using a carnauba-based waxes, hence not so suitable if that's what you're looking for. If for protection and the rest of other stuffs, I don't think there's any difference whether the colour is white or black...I mean clear coat is clear coat and they're the same regardless what the colour is underneath......
Budget?