is sdl+opengl slower than cocoa/carbon+opengl?

Probably not in any significant or measurable way. What is there to be slow? resizing or calling a swap buffer function?

SDL+OpenGL is Cocoa+OpenGL...

I dont know, I heard that glut (to do the window) + opengl is slow so I was wondering about sdl.

Both GLUT and SDL use Cocoa with OpenGL. However, there may be faster ways to implement it from what they do.

neither GLUT nor SDL is slow.

That said, it may be difficult or impossible to use some OpenGL features from GLUT (I can't comment on SDL) that can provide better performance. For example, creating a pbuffer context to avoid a copy-to-texture operation.

That's what EXT_framebuffer_object is for

You can often do extra things with SDL and GLUT by using CGLGetCurrentContext() at an appropriate moment, and modifying it. Yes, then you're into the Mac-specific stuff, but sometimes it's worthwhile.

The argument against GLUT is typically that it is a bit limiting in terms of windowing, input and generally behaving as a good application.

Buy the Quad 2.5 Ghz PowerMac G5 Sorry, couldn't resist.

But it follows my saying: If you can't speed up the software, throw
hardware at it.