Hey, first off congratulations on getting an offer for CompSci! As someone about to finish their CompSci degree, I've had a great time on my course.
For the accommodations, East Park is newer, so it's gonna be slightly more 'modern'. It also has En-suite options which Moberly doesn't have, but for Standard rooms they're about the same size (9.5m2). East Park is also closer to the Forum (central building on Streatham Campus). Moberly however I've heard tends to have a quite nice community aspect, since it's one of the smaller accommodations on campus, so you can learn and meet all the flats in your accommodation decently easily.
Hope this helps, and lmk if you have any other questions!