Yes, if they're on the same B.Net, then you gain all of the new features...

Things like a drop down box within account management, to manage each account quickly.
I'll need to log out of B.Net and into the next one (the same as everyone did prior to B.Net account implementation).
I'm pretty sure there will be other beneficial features to having multiple accounts on one B.Net; they're talking of making account bound items bound to the B.Net account (no clue if this will ever go in or not).

But one of the new features is one code per each account within one B.Net.
So approximately 30 seconds of delay for each subsequent account after each previous account.

It's a preference between the convenience of quick logging in (while retaining an authenticator) versus the new features which are being implemented.