According to the latest article on the Dolphin home page, nvidia cards got a major performance hit (plus some bugs) with the switch to an integer based graphics pipeline in the latest Dolphin releases, while AMD cards got a speed boost and better accuracy. So in that case, AMD cards are now way superior for emulating Gamecube, even though most games don't have that kind of gap.
For what it's worth, that article made me choose an R7 260x over a 750ti. The 750ti is both faster and more power efficient in most things, but Dolphin seems to now be heavily weighted towards AMD cards. Dolphin easily runs best in OpenGL mode (way smoother than D3D), and is faster in OpenGL mode, with similar performance to the old DX9 mode but a smoother framerate with less hitches.
As far as the drivers go, there's no reason to worry about AMD drivers if you're on Windows. On Linux, the drivers aren't completely horrible, but they are worse than Windows, and AMD has a tendency to drop driver support after a few years, which is really bad on Linux.
BTW, the latest AMD drivers (Catalyst 14.4) support OpenGL 4.4 too, but the most important feature for Dolphin was already supported through AMD's pinned memory extension way before it was supported on nvidia and OpenGL 4.4.
In personal experience, going from an nvidia card to an AMD card, AMD has more tearing with vsync off than nvidia does, and doesn't seem to acknowledge Dolphin's vsync in OpenGL. But you can set vsync and triple buffering through their driver control panel, which is sufficient.
For what it's worth, that article made me choose an R7 260x over a 750ti. The 750ti is both faster and more power efficient in most things, but Dolphin seems to now be heavily weighted towards AMD cards. Dolphin easily runs best in OpenGL mode (way smoother than D3D), and is faster in OpenGL mode, with similar performance to the old DX9 mode but a smoother framerate with less hitches.
As far as the drivers go, there's no reason to worry about AMD drivers if you're on Windows. On Linux, the drivers aren't completely horrible, but they are worse than Windows, and AMD has a tendency to drop driver support after a few years, which is really bad on Linux.
BTW, the latest AMD drivers (Catalyst 14.4) support OpenGL 4.4 too, but the most important feature for Dolphin was already supported through AMD's pinned memory extension way before it was supported on nvidia and OpenGL 4.4.
In personal experience, going from an nvidia card to an AMD card, AMD has more tearing with vsync off than nvidia does, and doesn't seem to acknowledge Dolphin's vsync in OpenGL. But you can set vsync and triple buffering through their driver control panel, which is sufficient.