Most of their solvent products are pretty good, I use a few of them on occasion. However, waxes for colours is marketing horse manure.
Don't forget that a wax is an LSP, so is designed to protect. AGHD should be fine on a 350 if you've been happy with it on the BMW, but how much prep work have you done to the paint before using it? Black can be a nightmare, but I've always found that if its been corrected as much as possible then the LSP lasts longer.
I prefer DJSN as my wax of choice, however I have used FK1000P before as well which lasts for aaaaaaaaaages. Right now I'm trialling Envy FA, on the Clio and the BMW, just to see how long it lasts. So far, it's outperforming anything else I've used in terms of beading and ease of cleaning. Not cheap, and maybe not what you're after, but I love it.
So yeah, DJSN for me. I prefer it to the £120 pot of Swissvax I've still got floating around...