More classes available, a larger faculty to draw from for research purposes, more peers and institutional focus on the program. In this case, likely also far better industry connections.
Search these for class offerings:
https://www.cs.wisc.edu/courses/current
http://registrar-prod.unet.brandeis.edu/registrar/schedule/classes/2018/Spring/1400/UGRD
https://www.brandeis.edu/computer-science/undergraduate/courses.html
Only 5 CS courses are required for a BA in CS at Brandeis as far as I can tell - the full degree is really hard to find. Compare that to UW-Madison which requires at least 9 courses for the BA as well as math. While not important like engineering, the program is not ABET accredited, suggesting likely a lack of either required math, physical science, or CS courses.
As with any case, fit and financials are important and both are good schools a CS grad will do fine at. But if all else is equal, I think UW-Madison offers a lot better resources for CS and a fuller curriculum.