Berkeley (L&S Undeclared) vs UIUC (Computer Science + Anthropology)? [CA resident]

There are plenty of STEM majors you could get into at Berkeley pretty easily - Math, Applied Math et al.

But if you want to have access to CS/DS courses its going to be pretty tough.

One trick you could use is to enroll in the CS/DS courses during the summer sessions when there are no enrollment restrictions - and it will be significantly cheaper than paying $75k extra at UIUC.