Especially on older cards actually! The new hardware, since the 3000 generation or so, moved some "secret sauce" (probably bullshit) into the firmware so that everything that the drivers need to do is something that Nvidia is willing to disclose, so there can be open source drivers that can get the hardware out of low power mode. That lack of "reclocking" crippled performance with nouveau.

Eh, I'd still buy AMD if possible.