If the two schools are tied for your first choice, and going to either of them would be comparable in your mind, ED II would have been ideal in my opinion.
I said would have because I seriously doubt they’ll let you change, and in all honesty, sending this email may look bad on your part, as it will appear you are unfocused, and unsure. In addition, they may think it is now your fallback, assuming you just got rejected from another school