Leeds is the better choice and better university on almost any objective measure.
SOAS is just a mad place and everyone in it is mad. If you are from out in the sticks and you're the only loon in the village and you want to come to London and wear mad things, protest to save the gay whale and have free Hare Krishna curry on Tuesdays, then there is no amount of Leeds that will make up for that.
My strong advice would be to go to Leeds, be a rebel there and then go to a better London university for postgrad or law school.