By the one that they gave you. The reason they gave that one was because they go by the size of the baby which is most accurate. You may find in the end they will guess wether you will go before or after your due date due to the size of baby.
Use the one that came from the ultrasound. (And don't worry, you won't be the first person ever in the history of maternity leave to have to adjust your dates if the baby does not come exactly on his or her due date.)
Definitely use the Ultrasound EDD,Your Midwife EDD isn't as accurate as the Ultrasound.