This ^
Maybe there’d be added prestige if you want to stay in the South but it seems like transferring from Tufts to Vanderbilt for “prestige” is a terrible reason.
Otherwise, the two schools seem very different in terms of culture, region, etc. I loved Tufts but can’t imagine that I would’ve enjoyed Vanderbilt as an undergrad (though I have a few friends and family who had a good time there as grad students or postdocs).