Hmmm . . . a tough decision for sure. Why would you limit yourself to just one brand?
Anyway, I haven't used the Optimum polishes, but I have used Optimum Car Wax. It's pretty decent, but it didn't last too long for me. The Optimum Car Wash (new formula) really is one of the best car wash soaps available IMO.
When it comes to Menzerna I've used pretty much the whole line FPII, Intensive Polish, Power Gloss, Final Touch Glaze, and FMJ. FPII IMO is one of the finest finishing polishes made IMO. It really leaves a fantastically wet, deep shine. IP is also an excellent polish, but it dusts a bit and has a very short working time. FMJ is a decent sealant and leaves a nice slick surface. PG doesn't really work well with a PC and besides it's REALLY aggressive so you probably don't need it. FTG is a good glaze, but IMO if you do a good job polishing there's no need for a glaze because all they pretty much do is fill imperfections.
IMO no one brand makes fantastic products from start to finish so to speak. This is one of the reasons I shop with AG. Their huge brand/product selection allow me to pick & choose among different brands to create my personal "ultimate detail kit."