It depends on how interested your ISP is in finding out if you're using Tor. In most cases, using any bridge should be sufficient, since the vast majority of ISPs are not spamming the BridgeDB to identify the bridge IPs. The purpose of an obfsproxy bridge is to defend against deep packet inspection, which is a way to fingerprint (even encrypted) connections, to determine what type of connection it is. obsproxy tries to look like another type of connection. There may be a couple dozen countries in the world where ISPs are doing that, and the victims of this censorship are a small minority of Tor users, but Tor Project gets paid to help those people, so we have obfsproxy. Now, the reason why I didn't give an absolute Yes answer to your question, is that apparently China is able to identify and block connections to obfsproxy bridges that use version 2 of the protocol. They've either figured out how to DPI the connection, or they blast suspicious IP addresses with random blocks of data and look at the response. So, it is possible to identify obfs2 bridges, and it could be possible to identify obfs3 bridges in the future. I guess then they'll come up with an obfs4 protocol or something totally different. It's a never ending cat and mouse game where they try to stay one step ahead of the adversary. But if you're in a western country, you're *probably* ok with any bridge. Well, you might as well go with obfs3 at this point, to future proof your setup a little.