University of Illinois at Urbana-Champaign vs UCLA: which is considered more prestigious for undergrad?

The biggest practical tradeoff is broad name recognition versus program-specific reputation. UCLA tends to carry more overall prestige in everyday conversation because of its national visibility, selective admissions profile, Los Angeles location, and strong reputation across many fields. UIUC, though, is exceptionally respected in several undergraduate areas, especially engineering, computer science, and some quantitative disciplines, where its reputation can be every bit as strong and sometimes stronger.

If you mean general undergrad prestige across the country, UCLA is usually the one people will see as more prestigious overall. It has a stronger all-purpose brand among the public, employers, and students who are not looking at a specific major. That matters if you want a school whose reputation travels easily even outside academic circles.

UIUC is not a step down in any simple way. In technical and STEM-heavy contexts, especially engineering and CS, it is often viewed as elite and may be regarded more highly than UCLA by people in those fields. So the answer changes a lot depending on whether you are comparing the universities as whole brands or comparing specific departments.

For a student asking only about overall undergraduate prestige, I would give UCLA the edge. For a student focused on engineering, computer science, or certain highly technical programs, UIUC can absolutely match or surpass it in perceived prestige within those areas.