I think this depends on the types of ECs you already have. If you don't have much clinical exposure, the clinic position sounds like a good option. If you don't have research, go with the research job. If you don't have either... then I personally would do the research position and try to find another clinical opportunity. There are so many clinical positions out there that don't require you to work full-time or possibility necessitate you spending an extra year in undergrad.
tl;dr - if I were you, I would take the research job and look for other clinical opportunities.