Currently, based on (1) price per hash and (2) electrical efficiency the best Bitcoin miner options are:
AntMiner S7
AntMiner S7 Bitcoin Miner
Capacity 4.73 Th/s
Power 0.25 W/Gh
Weight 8.8 pounds
Guide Yes
price $479.95
Earning /month
0.1645
AntMiner S9
AntMiner S9 Bitcoin Miner
Capacity 13.5 Th/s
Power 0.098 W/Gh
Weight 8.1 pounds
Guide Yes
$1,987.95
Earning /month
0.3603
Avalon6
Avalon6 Bitcoin Miner
Capacity 3.5 Th/s
Power 0.29 W/Gh
9.5 pounds
Guide No
Price $499.95
Earning /month
0.1232