please help me to make a choice between Mk5 and Mk6 (CF-19)

folks,
A few days before, i desided to buy a CF-19 Mk5(used of cause), and yesterday i found Mk6 with same seller. So not make me a hard choice between Mk5 and Mk6. i give the spec of the two model of the seller and price.

Mk5 Mk6
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price: $780 $940
CPU: i5-2520M i5-3320M
ram: 4GB 4GB
HD: 500GB 500GB
keyborad:...

please help me to make a choice between Mk5 and Mk6 (CF-19)