They are both fine. Your real question is whether or not you can better leverage LBNL or SLAC (ALS vs LCLS/SSRL). I think LBNL would be a bit better for optics specifically. If you need more compute access LBNL/Berkeley might be a bit better because of NERSC but it’s not a huge deal because you’d probably use NERSC anyway. Of course, it’s quite likely you could be be working with PIs from either university as well.

Stanford students are generally happier than Berkeley students (talking about PhD/Postdocs in particular)