A2 is the best in terms of hashrate and power consumption, but the price is very high.

Zeus, Gridseed, silverfish are good.

GAW just rebrands Zeus.

KnC...don't do pre-orders dude.

And if you are a newbie in mining, don't buy from these companies' websites, go to ebay or Amazon and buy some used miners. You are fully protected there.

My 0.02 btc:)