Biochemistry rules all the way. It definitely is thought to be harder, but I've done it and I don't think that it is much harder than biochem or premed. The best part about it is that it has much more scope than biomed or premed, seeing as both those are only useful if you can get into medical college after. If you're a 100% sure that you want to become a doctor, I'd still enroll in biochem and later on if you decide you want to switch it's very easy. It's harder to switch from bio med to biochem.. but from biochem to biomed will be a breeze... Good luck!!!!!!!!