The mistake you're making is in assuming the menus and the menu bar are using the same 'effect'.
Leopard still uses simple resources (small transparent PNGs) to build the actual menus then applies a subtle blur effect. The menu 'bar' no longer has a "resource", it is now built from scratch by the newesh '
CoreUI' layer and is more of a rendered surface, allowing for future support for resolution independence and possibly other fancy stuff (animated movement, animated icons etc.) yet to come. The 'translucence' which is actually done by sampling the wall paper and applying several techniques to it, including some subtle pseudo-3D real-time shading (the 'curved' looking surface), isn't really just "transparency and blur". At all.
On some GPUs that only partly support QuartzGL, all this work just to render the menu and draw everything on it in real-time full-color would require using the CPU fallback mode and just wouldn't be worth the resource use.
I hope this helps explain why your MacBook has less effects on it's Leopard Menu Bar. Maybe in the future the menu bar routines can be optimized to allow supporting more GPUs in real-time with the full set of 'effects' applied. In the meantime this is probably the best compromise while still allowing everything important to work.