I really don't buy that argument. The "optimized for performance" statement is pretty much a marketing ploy to downplay Microsoft (who doesn't make hardware, but that's changing).

The only argument here is for the GPU. Apple has put in a lot of work to maximize usability by targeting a specific GPU/CPU combo. RAM is a constant that doesn't really play into the design of the OS, since all RAM manufacturers make the same thing, but with different guarantees.

RAM is about the easiest thing to upgrade, second maybe to a hard-drive. This used to be trivial to upgrade, but now they're making it unnecessarily difficult to lock in customers to paying out the nose for something that should be a simple and cheap upgrade. They're operating on insane margins in the RAM arena (and CPU arena, but that's a different story).

Not sure what the performance or aesthetic improvement would be in this case?