^ I thought UoM undergrad had breadth subjects?
If you choose the same subjects, how can't you get the same things as biomed?
UoM biomed has course-specific units and programs that are restricted to students enrolled in that degree only - these are worth looking into as past students speak very highly of them.
(Edit: as per above 
)
IMO so long as you have the prerequisites, there are really no other considerations other than doing what interests you and gives you the most flexibility (and these factors are more likely to affect your changes of gaining admission). People obsess about "being prepared" for med and place that high on the list of priorities - IMO it's a somewhat misguided notion, a common one that biomed programs all over the country have capitalised on.
A good preparation for med is basic medical science (e.g. the MD prerequisite sequence) and a degree in which you have applied yourself, established good study habits and gained some insight in to yourself as a future professional, lifelong learner and scholar. IMO a decision to study undergrad biomed should be made according to an evaluation of one's interests and the curricula, not the dubious blanket claims that it is a better preparation.