Pick a distro you're comfortable with and you'll get to know its quirks and workarounds. I'm partial to Fedora Core 4_64 but not because of anything negative with other distros. Oh, I've used Slax, Xandros and Slackware but nothing recent and nothing 64 bit so it wouldn't be a fair comparison. Maybe if I had some time and a reason to I would check out some other 64 bit distros but no time and no reason. Fedora works fine for me.