It may depend on the major?
I think that the relative isolation of Boulder is a disadvantage compared to UCLA. For instance, our Colorado medical school, *(there is only one in Colorado), is all the way down in Aurora, making CU Boulder less strong for premedical students.
The teaching and research hospitals are all in Denver, or Aurora. UCLA in particular has an amazing medical program so the premeds get a lot out of an undergrad UCLA education. They can work in a teaching hospital part time, for instance. CU students can work down at Anshutz Medical campus in the summers, and often move to Aurora for the summer to do just that.
CU Boulder has less impacted majors, compared to UCLA, and smaller class sizes, which is considered a great thing by many CA parents who send kids this way.
Also, I see a lot of CU students getting somewhat useless majors, such as Integrative Physiology a "catch all " major for premed, pre dentall, pre public health, pre PT type of career goal, and that major now the largest number of students in Arts and Sciences at CU.
Also the drop out rate in CU Boulder Arts and Sciences is still relatively high. Leeds School of Business undergrads
CU Music, and CU Engineering have lower drop out rates.
With that, undergrad physics at CU Boulder is probably a tad stronger than UCLA because of JILA and NIST.
Chemistry and Biochemistry very very strong at CU.
Computer Science is really doing very well in ranks at CU.
Aerospace and chemical engineering have been very strong for years now at CU.
With engineering, overall, UCLA has an edge on job placement, although CU students can and will get jobs in Los Angeles when they graduate. Los Angeles has now surpassed Silicon Valley for jobs, so its a bit like comparing apples and oranges, to compare UCLA to CU Boulder. Boulder is a about 100,000 person town. Boulder is 30 miles north of a city, Denver of about a half million, with a million in greater Denver. Its just very very small compared to LA.