I would do the research at your home program since it's more applicable to what you want to go into and has a higher chance of getting a publication. Also, it means you wouldn't have to move over the summer which is stressful in itself. But make sure you talk to students that are currently in the labs or recently passed through the labs to see if the PI would be a good research mentor for you. During my M1 summer, I had the PI pull a bait and switch on me and had me work on a dead-end project that went nowhere, even though he promised "many publications". I'd also prioritize dermatology research, as it's difficult to match dermatology without specialty-specific research. You can always do cardiology research during residency when the time comes.