I would not worry about the differences, particularly if Nursing is what you’re looking for.
The key differences between UC and CSU is not their academic rigor, but their academic offerings.
The mission of the CSU’s is based on practical applications and non research-oriented careers. The CSU system awards mostly bachelor’s degrees, and no PhD’s by design.
The UC system is more research and theory-based teaching. Most professors engage in research, providing students with the opportunity to learn in a research setting. But the UC’s tend to be more graduate, rather than undergraduate focused. UC awards professional and doctorate degrees.
It’s important to keep this in mind when choosing between the CSU and UC systems. Neither is better than the other – rather, students may be more suited to a particular system due to their academic and/or career goals.
If your goals include Nursing, then you’ll see that the CSU’s have far more ‘hands-on’ opportunities than the more theoretical UC’s, and as such can provide you with the skills sets that employers will want.