Which is the Better Heatsink?

Which heatsink is better for cooling an AMD FX-8350 Cooler Master Hyper 212 EVO - http://www.newegg.com/Product/Product.aspx?Item=N82E16835103099&cm_mmc=SNC-YouTube-_-na-_-na-_-na

or the Xigmatek Dark Knight Night Hawk Edition - http://www.newegg.com/Product/Product.aspx?Item=N82E16835233029 

or any other suggestions?

Go with the Dark Knight, it's much better than the 212 evo

I can highly recommend the 212 evo, as can many because it's very popular. But I don't doubt at all that the dark knight could be better. It certainly looks better, and logan gave it a good review. Either is a good pick

+1 on the xigmatek, it's a good cooler, the hyper 212 is decent, but it's not a top performer by any stretch of the imagination, for the same price and format (120mm cooler), the Arctic Freezer A30 probably is a much better choice.

If your case is large enough, I would definitely consider a double heatsink 140 mm cooler like the Noctua NH-D14 or Thermalright Silver Arrow Extreme. The Coolink Corator DS is a budget version of the Noctua NH-D14 with a single impeller type fan, for when you need more clearance. The heatsink is made by the same factory as Noctua, Coolink and Noctua are two brands of the same company.

Also very important with the FX8350 is cooling the VRM MOS-FETs, they tend to run hot when overclocking. Sometimes a down-blowing CPU cooler is the better choice, depending on the heatsink on your MOS-FETs. If your MOS-FETs don't have a heatsink, get one, Thermalright has a nice single-piece heatsink, but you can also get individual high quality MOS-FET heatsinks from an electronics store (they have 3M thermal glue pre-allied to them, you just stick them on, it's cheaper than the thermalright heatsink).

Overclocking the FX8350 requires a very good cooler, it runs very hot and has a narrow thermal envelope.