I disagree because if you are best friends(BFF’s) with a boy, then, you can’t have so many things in common, and you cannot have fun sleepovers, gossip about things. You sure can have a great friendship, but it will never be stronger than if you have the same friendship with the same gender as you.
Imagine, your BFF being of the opposite gender than you. Do you think your friendship would be the same? Obviously not, because you don’t pass through the same problems, you maybe aren’t interested in the same things, same sports, same people. You are closer to a friend if you like some of the same things, if you have the same problems. When something different happens in your life, for example if you are a girl and your BFF is a boy, then, if your BFF has a problem, and you have never passed through that problem, you cannot help them, give them advices. This is an exception in some cases, if you have an older brother, he might help your BFF (of the opposite gender), but as I said earlier, it only happens in rare cases.