Is University of Illinois Urbana-Champaign or Duke harder to get into?

The biggest practical tradeoff is that Duke is highly selective across the board, while UIUC’s selectivity varies much more by college and major. Duke is a smaller private university with a broadly holistic process and a very limited admit pool overall. UIUC is a large public flagship, and while it is absolutely selective, the difficulty can change a lot depending on whether you are applying to something like engineering or computer science versus a less impacted program.

Duke is harder to get into. In most comparisons, Duke is viewed as one of the most selective schools in the country, whereas UIUC is better understood as a school with some extremely competitive programs inside a university that is not uniformly as hard to access as Duke.

That said, UIUC can feel just as hard, or in a few cases harder, for certain applicants because admission is often very major-specific. A student applying to a top-demand UIUC program may face much tougher odds than someone applying to a less competitive UIUC major. Duke does not usually have that same kind of major-by-major swing at the front end, even though some academic interests may still be more common than others.

If your question is about a particular UIUC program, especially in areas like engineering or computer science, then the comparison becomes closer and depends on exactly what you are applying for.