There's definitely a benefit to placing a decent telescope outside the asteroid belt. From Earth, we get a lot of light reflected from the Sun from dust orbiting somewhere between Earth and 2 AU from the Sun, which pollutes our space images - it's called the Zodiacal Light [0]. A telescope outside this light pollution would be able to see faint objects much more clearly and easily than Webb.

[0] https://en.wikipedia.org/wiki/Zodiacal_light