Which is a better performer? (oc settings)

[CrazyCactuaR]

Computer Spec:
Asus P8Z77-V Deluxe
Intel i5-3570k @ 3.40ghz
Golden Empire CL9-9-9 D3-1600 2x 8gb memory

Hi all, Noob question here,

I seem to have two options with this motherboard i can either use;

a. 4.2ghz and 667 Mhz ram frequency
or
b. 3.8ghz and 800 Mhz (xmp) ram frequency.

I'm not entirely sure if i can use the highest of both until i play around more in bios but my question is, which (a or b) is better to use for performance?

Thank's all.

 

[Shiari]

Higher clock is better than faster ram. So, (a).