what do you mean by competitive specialties in the context of premed
Goro is more referring to the way that it's looked at from the perspective of a medical student applying for residency.
All research is able to be used - and is weighted close to equal - in the evaluation of medical students for residencies. You would have a competitive advantage applying for specialties in medical school if you focused your undergraduate research accordingly, if that's something you actually wanted to do.
My understanding, for medical school admissions, is that it doesn't really matter. Do something where you can be involved. Above all else, admissions like to see
independence. Being seventeenth author on a paper means nothing, but giving a poster or an oral presentation which you, presumably, have taken the lead on, is a big deal.