Medicine = being a marathon runner. You have to grind for a long azz time and there are so many "exit points" where you just may quit. Lots of weed out. You have to be smart but the key is persistence and work ethic.
Engineering = sprinter. You'll probably learn very quickly if you're cut out for it.
Several good friends are engineers (software, electrical and petroleum). These are the kind of dudes that could ace Calculus 1, 2, 3 etc, without even showing up half the time. Math is easy for them...they just have to learn and apply all the other concepts that come with engineering.
If you're struggling in Cal 2, intro to circuits or some other intro class....you're already behind.