There’s nothing wrong with starting to memorize early (but don’t put off practice just to do this). Just because you will eventually forget something doesn’t mean you won’t retain it better the next time you memorize it. In fact, “spacing” your studies and revisiting the material reinforces your memory of it.
Both have value, so you should memorize and practice. Memorization improves recall, and practice makes perfect (or at least improves your chances of passing the bar exam).