I think you can probably find your tribe at either school, so you may want to look at some hard numbers. Here’s a little link to some fairly current top-level comparisons of the UC’s:
https://www.thoughtco.com/comparison-university-of-california-campuses-786974
I would especially look at 4-year graduation rates. What this tells you is that it’s probably to get the classes you need, on average, at UCSD with a 59% vs. a 71% for Irvine. If getting in and out in the shortest amount of time is important to you, this statistic should be considered. I do not know if the stats exist for specific major, but it looks like the engineering majors tend to skew UCSD a bit lower.
You really should make an attempt to visit both campuses before making a decision. They each have their own look and feel. Both are very highly ranked as national public schools.