Should I use University of Illinois Urbana-Champaign or Cornell as my reach, target, or safety school in my college list?

The biggest practical tradeoff is that Cornell belongs in the reach category for almost every applicant, while UIUC can range from reach to target depending heavily on your major, residency, and academic profile. Cornell is an Ivy with highly selective admission across its colleges, so it should not be treated as a target or safety. UIUC is much more variable: for in-state students and less impacted majors, it may be a realistic target, but for highly sought-after programs like engineering or computer science, it can also act more like a reach.

For list-building purposes, Cornell should be your reach. Even very strong students with excellent grades, rigorous coursework, and strong activities cannot count on admission there. It is not the kind of school to place in a balanced list as a target unless you are using the term very loosely, and it is definitely not a safety.

UIUC requires more nuance. The school admits by major in many cases, and some programs are far more competitive than others. A student applying to a less selective major, especially from Illinois with strong academics, might reasonably classify UIUC as a target. A student applying out of state to engineering, CS, business, or another high-demand program may need to treat UIUC as a reach instead.

So the cleanest way to think about it is this: Cornell is your reach, and UIUC is somewhere between target and reach depending on the program and your context.