Both schools will offer you the opportunities and resources to be a successful premed, whether you do so is much more on your efforts, much less on which school you attend.
As to “cooked”: let’s say 250 students start as premed, 70% change their minds for various reasons (eg grades), leaving 75 premeds who get to point of applying. Of those that apply 30 get accepted. School proudly states in glossy brochure that 40% of their premeds got into med school.
I don’t know much about UMich, but I know at UCSD you’ll be often sitting in premed classes of 200-300 very bright students, all competing for say the 15-20% of the As the prof hands out, most students will get Cs or worse. The weeding out will be brutal.
Agree with @ gumbymom above.