Diffrences

8GB {2x4GB} 1600 MHz 9-9-9-24 @ 1.50v Rs :6565 {US $ 105} Vengeance
8GB {2x4GB} 1600 MHz 9-9-9-24 @ 1.65v Rs :5775 {US $ 100} XMS

In your region you're being screwed on the price for the Vengeance, and the other big differences are the voltage and cooling fins. The Vengeance is better of the Sandy Bridge CPUs {LGA 1155}. So if your MOBO can support the 1.65v then clearly get the XMS.
 

rooney10

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Feb 7, 2011
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my CPU is i5 2500k and mobo is lga so which mobo should i get?and which ram is appropriate?
 
The LGA 1155 supports both 1.65v and 1.50v, but the SB CPU IMC is better with 1.5v RAM.

As an alternative look at the G.SKILL 'Ripjaws X' series. Either get 1333 MHz CAS 7 {or 8} or 1600 CAS 8 {or 9}. Lower tight CAS is better; example CAS 8-8-8 is better than 8-9-8 or 7-8-7 especially in RAM 1600 MHz or slower. Benchmark testing is the only certain way of know the 'fastest' RAM.

Good Article -> http://www.bit-tech.net/hardware/memory/2011/01/11/the-best-memory-for-sandy-bridge/1