What matters is the asic technology and clock speed.
Cointerra and KNCMiner are the best ones right now because of their 28nm asics. With those you can get 1-1.2 Watts/GH.

BitFury, Bitmain, ASICMiner are using older asics.

KNCMiner will start shipping in 3 months its Neptune (20nm ASIC). That is the only product with 20nm planned for 2014. It aint cheap though. $10k for 3TH @0.6-0.7 Watts/GH.
Here is a review of KNCMiner and their products if interested.