Hm. What I think a job says, is probably not what the average premed thinks.
A job, would show me that you know how to be professional, work with others, etc. You know how to show up on time. You know how to handle challenges with coworkers and your patients/clients. You know how to work as a team. You may laugh at this but MANY med students have lived without having a real job. (No, I mean a serious job, not like being a lab tech were you choose your own hours to run a PCR-that said there are some serious lab commitments too...) Those are very good qualities to have when anyone looks at you for admissions. Why? Because being a physician is a job.
Volunteering, helps me understand how much you really want to get to know your patients, and the general field of medicine as a whole. I like to see if a volunteer just clocks hours, or at least has an understanding of how his/her unit on the hospital works, or can tell me several stories of patient interactions they've had, because ULTIMATELY, AS A PHYSICIAN, YOU'RE INTERACTING WITH PATIENTS. (sigh, i interviewed someone who said, "I don't want to see patients unless I absolutely have to," ehhh...did you not read the job description?)
As far as clinical jobs go, (I had one myself) I don't think it REALLY makes you stand out. I think it's what you say, what you learn, from your jobs that really makes you shine. If you can say you can draw blood, whoopdeedoo. Oh, you've done CPR? who cares. But, if you can tell me a reflection on what its like to do a procedure, and think about what the patient must be experiencing when you have to draw blood (and say your patient hates needles), or can speak about how futile CPR actually is, then we're talkin. Otherwise, you're just like anyone else just trying to pad your resume. Because those tasks, are done typically by PCTs or MAs. you're not applying to be a PCT, or MA, you're applying to be a doctor. Its good to appreciate what people do in your field as a whole, so job experience is great, but honestly, me working as a receptionist at a clinic meant more to my application than my clinical job being an MA.
So, whats my answer to all of this? Do both. Find a job you like to do, and no it doesn't have to be "clinical." Just have a good reflection off of it, and think about how it'll affect you as a future clinician. I can't imagine volunteering a hospital takes up that much time-4 hours a week at a hospitals PACU, ED, medicine floor is plenty. If you REALLY have difficulty giving up 4 hours (For most, I seriously doubt it), then cut facebook, cut SDN (for a bit), and maybe go to a few less parties and sober up some bit. Hate to say it, but you can get QUITE busy when you're in med school and even more in residency. Toughen up.