When you say that you will be paying $7K a year - what does that look like? Will you be borrowing the money, will your parents pay, will you cover out of pocket? Will your family struggle to pay that $7,000 a year, or will it be easy?
I’m a big advocate of following the money when it makes sense, and Brown for no personal contribution is a pretty awesome deal. But $28K isn’t that much to lay out for an undergrad education (in the grand scheme of things) and you sound like UCLA is where you really, really want to go. Brown is theoretically stronger for undergrad - but I honestly don’t think that matters that much, because UCLA can get you where you want to go. It’s a well-respected university and a place recognized as a good place to do undergrad. On the other hand, $0 is better than $28K! And Brown is a really strong school.
I don’t think living further away from home necessarily broadens your outlook more than living close; I think it kind of depends on what your experiences were before you go. For example, a CA student who lives 3 hours away from LA in a rural part of the state, and who has never been to LA, could have their horizons equally broadened by being at UCLA or at Brown - it’s all the same to them; the simple fact of closer geographic proximity doesn’t make the environment any less new or different. That said, I will say that coming in with the premise that you will go home and hang out with your HS friends a lot does throw a point in favor of going to Brown. Being able to go home is really nice! But you don’t want to go home too often. There’s nothing wrong with maintaining old relationships, but that plus the fear that you won’t meet new people who are as great as your current friends means you run the risk of closing your ecosystem and not branching out. College is as much about branching out as anything else.
That said, you have some time, so I’d sit with it. Imagine for one full week that you’ve made the decision to go to Brown - how do you feel about it? Also, can you visit? I would strongly encourage visiting Brown - it might be different than you think.