[CentOS] C6 or C7 for an old netbook

I've got an old HP Netbook, which is just fine for taking with when I'm travelling, to check email and news. I have a very old Ubuntu netbook-remix on it, and it really, *really* needs to be updated to something current. I, of course, would prefer CentOS....

The question is: I see that *if* the specs I just looked up (I'm at work, not home, where I could just turn it on, but they sound right) Atom N270 CPU, 2G RAM, 160GB drive - what should I put on it, C6 or C7? Upgrading the memory's not going to happen, so it's got to live with that size.

Opinions (please, no flame wars), just what will be most responsive on a machine this small?

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