For me it was completely different from o Chem. The material is different and it's less mechanism oriented. O Chem is more understanding what electrons will do and understanding basic chemistry concepts, whereas I found biochem to be a lot more blunt memorization. There was a large volume of information in my biochem class and you had to know things in extreme detail. But that probably depends on your professor more than anything.
So to answer your question - biochem will be harder if you aren't very good at memorizing lots of material in detail. But again, this is just my experience