Prestige is still important in public interest depending on the type of employer. However, a huge debt load without a good LRAP program will effectively prevent someone from doing public interest. So if you are absolutely sure you want do public interest (and I'm usually skeptical of college students saying that but someone with your experience should know for sure by now if public interest is for you) then less debt might be the better choice. Of course that depends on what kind of public interest you want to do. Of course federal clerkships depend on prestige, credentials, etc. but it's certainly possible to get a federal clerkship, albeit probably not one of the more prestigious ones, coming from a 2nd tier school.
I guess it depends on what kind of public interest you want to do.
BTW, does UCLA have a good LRAP program?