Readers I need your help! What book format do you like?

I'm writing an historical fiction and have a strong outline of my ideas but I can't decide if I want to write this novel in diary format or first person. I love the idea of both. What do you think? Do we enjoy reading diaries or rather it be first person? Now there are going to be the main character but some scenes are going to be different people. So In the diary I would make those other peoples perspectives into letters and maybe the other characters own journal.