Which is better? 1 8GB stick or 2X(8GB)?

[Jirsis0217]

I was going to upgrade to some more RAM and I am thinking about getting either this
Crucial
Ballistix Sport 8GB DDR3-1600 (PC3-12800) CL9 Dual Channel Desktop Memory Kit (Two 4GB Memory Modules)
-http://www.microcenter.com/product/382101/Ballistix_Sport_8GB_DDR3-1600_(PC3-12800)_CL9_Dual_Channel_Desktop_Memory_Kit_(Two_4GB_Memory_Modules)
OR
Crucial
Ballistix Tactical 8GB DDR3-1600 (PC3-12800) CL8 Desktop Memory Module
http://www.microcenter.com/product/385179/Ballistix_Tactical_8GB_DDR3-1600_(PC3-12800)_CL8_Desktop_Memory_Module

Would it be better to get one stick of RAM or two? Or does that make a difference at all?
Or for $5 more I could get this
Crucial
Ballistix Sport XT 8GB DDR3-1866 (PC3-14900) CL10 Dual Channel Desktop Memory Kit (Two 4GB Memory Modules)
http://www.microcenter.com/product/415423/Ballistix_Sport_XT_8GB_DDR3-1866_(PC3-14900)_CL10_Dual_Channel_Desktop_Memory_Kit_(Two_4GB_Memory_Modules)


Thanks For Feedback!
-Jirsis

 

[Tradesman1]

A 2x set is better, allows for dual channel ops, which can provide a 10-15% performance increase