if you want wax that lasts, you need to buy a sealant type wax. Klasse Sealant glaze is the best of the best. they actualy sell those at my local bmw stealership, so they might have it at yours? if you want a wax that looks good and easy to apply, use the pure carnauba.
the sealant glaze, as some say, does not provide a "deep" and "wet" look as well as a pure carnauba wax. so you can make a choice of what you want.
another alternative is to first use sealant and then after a week. apply carnauba (of course wash the car first).