If i'm going on the pre-med track but is deciding both medical and vet school,....?

All volunteer work will be good. Med schools like to see a well rounded applicant.

Realize that veterinary medicine is not a wise choice right now, unless you plan on specializing. Limited jobs compared to the number of grads. Pets are a luxury. More and more disgusting people are choosing shelters and death shots to veterinary care.

Edit: I haven't heard anything about publication during *undergrad* being a huge 'must have' for all med schools. Plenty of residents are published and it can help with landing work post-residency and if you are lucky enough to be published during undergrad, yes, that will help for med school. But, I can only speak as to the grads and residents that I have conversed with. For them, it's about being a well rounded applicant. That's volunteering, extracurriculars, and excellent grades in ALL coursework, not just PreMed.
Having your name on actual published work is a difficult thing to do during undergrad - most of the folks getting second or third billing on true publications are grad students and residents, not undergrad lab rats. There just aren't enough legitimate research papers published in legitimate peer reviewed journals that would even involve undergrad students to the point of getting credited to make it a requirement. If you can get one, great. If you can't, then you focus on the other stuff. If it becomes a major concern, start contacting schools and asking what they are seeing on actual accepted students' applications.
It's certainly a bonus and would put a gold star on your application and I would not dispute that at all, assuming it's a legitimate peer reviewed published research project.

It is the least important thing you can do - compared to getting top of the line GPA and MCAT scores * and * getting a research paper published.

Everyone volunteers. Everyone cleans the beach. Everyone transports patients at the hospital. Everyone serves the homeless. Everyone builds a church in Mexico.