Shadowing is irrelevant for applying to undergrad, maybe with the exception of a BS/MD program. Go for the research opportunity.
The only way that clinical experience would be relevant for applying to undergrad is if you were doing something that in and of itself showed something about you - for instance, if you’d gotten a CNA or MA certificate as part of your high school program, and were working in that capacity in a field that you were passionate about. An example might be having an ultimate goal of becoming a geriatrician because of having grown to love caring for the elderly while visiting your grandparent in a nursing home, gotten the CNA/MA in a high school course, and started working in a nursing home part time during the school year, and full time this coming summer, because you loved working with that population. THAT would be a relevant experience for college applications, because it would show focused drive and determination towards exploring your passion, your intended life’s work. Not that being a CNA is a path towards becoming a physician, but it would demonstrate that you are serious about becoming a geriatrician, have some experience working with that population.
All that shadowing a surgeon as a high school student says about you is that you had a connection that would allow you such access. Go with the research opportunity. It should at least produce a letter of recommendation that says something about your contribution to the research project.