I would like to draw an interface with knob, similar to "overdrive" (green) in this photo:
In iOS, such as vector graphics should I use? Quartz, OpenGL ES, or something else?
I'm sure can be done with OpenGL, but I think it's very complicated. So if you can I would avoid it using something more "simple."
It depends to a large extent how the rest of your GUI is rendered. However, unless you're already using OpenGL, Quartz or CoreAnimation are probably your best bet.
Looking at the screenshot, it seems you could probably achieve the effect with two image layers, a background (static) and a foreground (rotating).
The background image could have the scale (painted on the pedal) and shadow, then the black knob border and shiny metal middle. Then you can just draw the black tick mark indicator at the appropriate angle, either using Quartz or using a CGLayer and rotating it (especially if you wanted to have part of the button texture rotating with it).
It looks like the knob is smooth, so you don't need to worry about rotating the edges. And assuming the light source is fixed, the highlight on the top-left edge and the shine on the metal middle can be static too.
However, if you wanted to be more realistic, you could try having a third layer with just the shiny middle, and rotating this back and forth slightly to animate the knob middle as the pointer rotates. It doesn't need to go around all the way; maybe 10 degrees or so of variation should help sell the effect.
