The Mac Studio (at least the M3 Ultra model) blows the Framework out of the water when it comes to AI performance, though, at least according to this (Dutch language) benchmark: https://tweakers.net/reviews/13614/framework-desktop-de-fram...
Paying twice the price for twice to seven times the performance may not be such a bad thing. Then again, with Apple you're kind of stuck with macOS and the like, so Framework may still be the better option depending on your use case.
The M3 Ultra also consumes a lot more power because Strix Halo is actually a chip for laptops. The Framework here is a desktop but that doesn't change what AMD prioritized when building this chip.
The M3 Ultra is more efficient both on the CPU and GPU side.
I'd hope so since M3 Ultra is using a newer/more efficient manufacturing process than Strix Halo!