Yeah, from what I can gather about med schools, they really don't care if you get healthcare experience by volunteering or by having a job related to the field as long as you show commitment to the field. I'd definitely say to find some volunteering somewhere if you're going to take the other job to show your dedication to the field.
The only advantage to actually getting paid to do healthcare jobs is that you normally can actually DO more with the patients than you can when you volunteer. So I volunteered for 1.5 years in a hospital and 6 months with a free clinic and never had any real hands on experience with patients except to talk to them, push them around in wheelchairs, and when the supervisors weren't looking, take vitals. I got a job in a derm office for 6 months and was drawing blood, charting, writing rx, assisting in surgeries, administering local anesthesia, taking vitals etc. Because of the experience, I had a lot more to talk about in my interviews. 😛
And whether or not it helped me get in this year, I have no idea. I didn't get in anywhere last year and got accepted to 3 D.O. programs this year with no change in my grades or MCAT and only the new job. But then again I didn't apply D.O. last year cause I didn't know it existed! Good Luck either way!