Nearly all of my books are written in 1st person, quite a few of those in 1st person present. When I choose to tell a story this way I want the reader in all of the way. I don’t give the reader’s mind room to wiggle out of the story. When I choose 1st person past, it is often because I’m uncomfortable asking the reader to occupy the shoes of the narrator with the immediacy that present tense demands. When my narrator is living through a story that is simply too impossible for young readers to inhabit without undue pain, I often remove them one step by using past tense. This way they know the protagonist survived to tell the tale. In 1st person present the reader isn’t given that guarantee. It was important to me, for this particular book, knowing the audience would be a little older, a little more mature, that they had no guarantee of how this story was going to work out.