Firstly, it's a bit silly comparing the two institutions because their goals are different. The BNU degree aims for fluency in Chinese; the SOAS degree aims for a rounded knowledge of modern chinese language (including both traditional and simplified characters), classical Chinese, philosophy, history, art, literature, etc etc. The classes offered at BNU in things like classical Chinese and history taught in Chinese, so they are superficial at best for someone who has just started learning the language. It's not the same as an academically rigorous programme.
BNU is a great place to study Chinese language. In fact, I'd go as far as to say it might be the best place in mainland China. And that's why SOAS students go there for a year! However, it does have its weak points. The examination system is atrocious. Cheating is rife. The exams are very easy to pass (and even score very highly in). For that reason, SOAS makes students sit their exams as well. The difference is....shocking. I'd say the SOAS exams are roughly twice as hard.
The BNU texts are very dry and boring. All of them are about how great China is (usually in terms of economy). I still cringe everytime I hear the phrase "经济发展". A whole year of it did my head in. I simply can't imagine 4 years of it. That reason alone would stop me doing a degree there.
About the cost. Well. In England we're entitled to government loans to help us go to university. In China, we're not. Your bro would have needed a fair bit of money to live and study in China for any amount of time. It's actually illegal to work on a study visa, so you might want to keep that one quiet.
I can't really think of anything else to say. It's a shame that you've formed an opinion so readily of everyone doing Chinese at SOAS (and indeed anyone studying any language in their home country...) based on what your brother said in private. I bet he didn't realize you'd go blabbing it on an internet forum.
They're both great places to learn Chinese. It just depends what you're after, really. I definitely would not rather study for 4 years at BNU than at SOAS.
Anyway, I hope this clears things up.