Is there any advantage to doing research at your own medical school vs doing it somewhere else (i.e. a different institution at a different city)? What about doing a research program vs just finding a PI yourself and setting something up with them?
It's probably easier to set up at your own institution, easier to find a positive mentor at your institution, you could extend your project as you have time in MS2-MS4, and there's less hassle with moving.
The advantage of doing research away is that you'd meet a new set of people and a new campus, maybe explore where you'd like to do residency.
Doing a research program has several advantages over arranging your own experience. There are generally some didactic component, there's a formalized curriculum, there's a name/rep associated with it, and there's support staff. Support staff is important when you're not getting along with your mentor or you're somehow not getting what you want out of the program. That's when you can talk to the program director and get help.
Doing it yourself might
give you more freedom in arranging who you work with, but funding becomes and issue (and as a med student, unless you're working ~2 hrs a week or less, you should