I'm certainly closer to my friends than I am to some of my family and my family is relatively small and relatively scattered compared to a lot of families. I only really feel close to my parents. By and large my friends have been there for me over the years though and I'm closer to them, can tell them things, do things with them, understand them and be understood by them more than most of my family.
The difference lies in something more primal I think. It's very, very, very hard to abandon family, harder than friends - no matter how close you are. Even if you fall out there's some sort of bond or societal expectation that family HAS to look out for each other.
So, I wouldn't say the two are equivalent, but close and probably closer with every passing generation as family loses its societal legitimacy - up to a point - and the people you choose to associate and share with take more and more primacy.