I never post on anything, but I remember how hard it was to find out about seminary, so I’m glad to offer my help. From a bnos sara point of view, I would say that bnos chava is more of a sophisticated intellectual- and growing- type, while bnos sara is more simple, and smart with a desire to grow and learn. Doesn’t mean nerds, just confident with who they are.
Classes, from what hear about BC, seem to be pretty similar, same with open mindedness. Bnos sara girls, possibly take school rules, etc, a bit more seriously (though such things change from yr to yr). Basically, I was no where near a jap when I came into bnos sara, but I learned to be much simpler and care less about styles etc.
1 more point, bnos sara is smaller. Many girls would go away for shabbos with anyone, even not from their close group of friends. So if you think you would gain from the closeness and warmth, it’s definitely a nice plus.