Which Book to Submit?

To those of you who have entered writing contests. I have two books in the same series that published this year. Both are eligible to submit to a contest I plan to enter. I guess it makes sense to submit book 1, but book 2 is even more exciting to me, personally. But book 1 builds the world and characters. I probably need to go with book 1 but I thought I’d ask for confirmation/advice here.