Hi, maybe to give you an inside opinion on this I could lend a hand. I am in the Electrical and Biomedical Engineering program at McMaster and one of its advertised features is its prerequisite coverage for medical schools. The program itself is fairly small (~30 people/year) but most entered the program with the medical school dream at the end of the tunnel. It's tough to say how many are actually still interested in that option as it truly is a daunting workload.
Without going into the details too much, I have spoken with a number of friends in the Health and Life Sciences and it seems as though their workloads are also heavy but in a different sense. Engineering has a crapload of theory that needs to be taught before you can apply it, which is why it is known for being so heavy. The Sciences allow you more freedom in with electives and really giving you more of a chance to develop your soft/communications skills. These really prepare you for the type of situations more commonly found in a medical atmosphere.
Unfortunately, due to the volume of applicants medical schools do still rely on marks heavily for acceptances. MCAT scores and interviews are crucial as well but they need to see where you stand academically from your undergrad which is why going for top marks is important. Less of a workload gives you more time to excel at your courses.
All in all, if you are set on medical school do yourself a favour and go through the Science route, but if you are the slightest bit unsure and are interested in applied sciences, engineering might be for you.
Electrical & Biomedical Engineering '13
McMaster University