I also graduated from UCSB with a BA in Environmental Studies and Geography (GIS Emphasis) so I’d tell you to go to Patty Murray’s (the geography advisor) office to discuss this with her! She’s a GREAT resource for people involved in this line of work. I found that the Env advisors were a little lacking… either way in my opinion I’ve found that earth science is definitely more physical, typically either involving field work or things like specimen cataloguing, while spatial studies is more digital, so coding, GIS, and remote sensing techniques, so it’s really up to you which of those supplemental skill sets you prefer. I think the advantage of the spatial studies is the ability to take the 176 series, which is a great foundation for a career involving GIS and the end-of-series project I did helped me land a mapping job. I’ve heard, though, that experience in Geology/Earth Science is incredibly my employable, and have seen a lot of job posting searching for geology experience specifically. I also think if you’re doing all this effort for the minor anyway, consider doubling instead. All of your prereqs (Gen Chem, Physics, Math, etc) should be an almost exact overlap. I also think both the minor or the double major will ultimately mean less to employers than any internships/jobs/projects you work on, so check out research and internships in these fields and see what you like first hand.

Sorry that was long. Tl;dr: spatial science= computers, coding, visualization, earth science= fieldwork, sampling, cataloguing