It's not really about one being better than the other, just that they're designed for different purposes. Euclid is a survey telescope built to research dark ma

It's not really about one being better than the other, just that they're designed for different purposes. Euclid is a survey telescope built to research dark matter, for which it has a large field of view so that it can build up a picture of the entire sky in all directions. JWST is focused more on investigating the early universe, for which it has a much larger primary mirror (gather more light), but has a lot of other capabilities as well. Euclid has a much smaller primary mirror, and its spectroscopy capabilities are limited compared to JWST (it doesn't need all the same bells and whistles). It also can't observe as far into the infrared as well as Webb. However, as stated, it has a wide field of view and enough photometric color and spectroscopic resolution to do it's main job of measuring galaxy shapes and positions and their redshifts in support of investigating dark matter.