You can’t compare these ones.
Graphics cards handle high-level primitives like “draw a line” or “display a icosahedron with Mona Lisa painted on each face”. Their ability handle these primitimes instead of handling them in CPU is why their performance is important.
Now, sound cards basically just inputs and outputs audio. Very simple task. They do this more or less effectively, but differences between them are nowhere near compared to differences between craphics cards.
This of course changes, if you have a soundcard which has some processing power built into. Then they are able to handle high-level primitives like “process audio with plugin X” or “mix these audio streams into 5.1”. In this case there are huge differences between models.
But for basic audio interfaces the quality differences can be divided into these categories:
- How well programmed is the driver. This has effect on stability of the driver (no crashes) and how low latency you can get.
- Clock, converter and analog circuit quality. These dictate how good sound quality you can get in/out of the interface.