Internal medicine LOR?

I know threads have touched on this kind of thing before, but I'm in need of advice for my particular situation. I'm going to have four letters available to send to programs - 3 ortho (including chair's) and 1 internal medicine.

I know the mantra is to send only ortho letters, but I feel like this medicine letter may be the strongest one I get in terms of personal qualities and work ethic. I was on an inpatient team with this attending for two months on my medicine clerkship, and I received very positive feedback from her at clerkship's end.

That's not to say my ortho won't be good. I think they will be, but I've heard it's best to send only 3 LOR's if the program asks for 3. So, is it safe to send this medicine letter as one of them or should I opt for all ortho? Are there certain types of programs that would be more/less cool with a medicine LOR? Thanks a bunch for the help.

As a rule, I would send the ortho letters unless a program allows for extra letters or specifically requests a non-ortho letter, no matter how strong that letter might be. People in ortho know each other, either directly or indirectly, and are at the very least able to judge the ortho letter relative to previous letters or personal acquaintance. Everyone who is going to match successfully has good letters... the only way they can be evaluated is relative to each other or a known standard. the chances that someone reading your medicine will know enough about that attending or medicine service to judge the letter are pretty slim, so the letter is much less useful.

That being said, if you think an ortho letter is so-so or unflattering, you may want to use the medicine letter instead.