Most of the benefit of logging in is for manufacturers.
Production Utility (in Tools) requires being logged in. Production Utility does link the serial number to a manufacturer, so that when you click Get Information, it will say the name they entered for their account as who it was produced by.
On request, we can also mark an account's manufacturer profile as 'confirmed'. Doing this makes it say "Confirmed" in Get Information, which serves as a bit of a 'genuine check' for the mod, instead of just for the board.
I'd add some user benefits to logging in if I could think of any to offer.