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When I installed this I used ext4 as I thought I remembered that it was supposed to be the most up to date, but I don't really know if that is true, and I also don't know if it applies to Debian even if it is true for Ubuntu based OS'es?
I think ext4 is the way to go. It's the newest stable filesystem, and should be the default for modern distros. There may be other filesystem types on the horizon, but they're not ready for prime time yet.