Wait, let me get this straight, you did a meet today, and your doing a meet tomorrow?….
That makes little sense to me.
Anyways, it really depends on your turnover. If you have alot of endurance, and your 800 PR is more towards the sub 2 range, I would go there. by your PRs I would go with 400, but I dont know what you run in the 800. it really depends on you and your training regime. You shouldnt get too specific too quick, since the 400 and 800 arent that different until the very end. Id say run a week or two more without deciding and in the end, if you have more fun with one and you are just as good in both, I would choose that one.