12GB triple channel or 16GB Dual channel?

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Unless you know specifically that you will be running one of the relatively few professional-level programs that will use large amounts of memory, both of those are overkill.

However, to play along ... assuming you already have an X58 mainboard and are simply deciding on whether to get a three-stick kit or a four-stick kit, I recommend the three-stick kit. With any setup over 4GB of RAM, I will usually recommend using the maximum number of memory channels, even if it means having less total RAM.
Unless you know specifically that you will be running one of the relatively few professional-level programs that will use large amounts of memory, both of those are overkill.

However, to play along ... assuming you already have an X58 mainboard and are simply deciding on whether to get a three-stick kit or a four-stick kit, I recommend the three-stick kit. With any setup over 4GB of RAM, I will usually recommend using the maximum number of memory channels, even if it means having less total RAM.
 
Solution