cooler master v8 vs. v10

i have intel core i7 920 that works default 2.66 ghz.
i want to overclock it to about 4.2 ghz!
i dont know what to buy: cooler master v8 or v10?
v8 costs 55 eur and v10 costs 120 eur.
i dont see much difference except the price, i would prefer v8 because its much cheaper but i saw in v10 there is something like ram cooling, what should i buy?

The V10 has a peltier module for active cooling, it eats up a bunch of power to pump heat around. It does actually work, but the xigmatek hdt-1283 and sunbeam core contact freezer beat the V8 (and V10, sometimes) anyway, while costing a lot less.