If you wish for spacious and modern accommodation and ensuite facilities, bear in mind that these are not generally available at Oxford. Colleges tend to have a mixture of old and new accommodation, and only some of the rooms have en suite bathrooms. Some rooms are big, some are small.
Every college that offers law is good for law. Every college has a strong alumni network, societies (NB many societies are university-wide), and good tutors.
Magdalen is led by Dinah Rose KC, arguably the best barrister of her generation. She read Modern History at Magdalen before becoming a lawyer, and is about half way through her term as President of the college. Jonathan Sumption is a Fellow of Magdalen.
Christ Church is great, but can be inundated with Harry Potter tourists,who might sometimes get on your nerves.
If you go to Magdalen, you will spend the rest of your life telling people "It's Maudlin, not Mag-dah-len". If you go to Christ Church you will tell the rest of your life telling people "It's Christ Church, not Christ Church College", and explaining that a Student is a Fellow. Toss a coin.