As of right now, the S7 and the Avalon 6 are the best available.
The B-Eleven should be showing up for sale very soon - there's evidence it's in production but filling those sorta-cloud preorder contracts first.
Hard numbers on it are a bit iffy at the moment, but it should at least match the S7 on efficiency.
Yes B-Eleven supposedly started running for Hash Investers on the 11th, first payout is on the 18th. It will be possible to do some calculations once the payouts start as to the actual efficiency. Hopefully they full produce a full spec and pricing for units in the next Month or so?
Rich