It doesn't matter when it comes to your stated primary use. Either will work fine.
However, I quite like Windows 8 on my HTPC. It is, by no means, perfect, and I do NOT like it on my desktop PCs (though I might finally jump with 8.1, we'll see after I play with it a bit on my HTPC), but on the HTPC some of the Metro apps are actually pretty nice. I wish more of them supported better keyboard-only navigation (with consistent behavior), but the tablet-focused design actually works pretty well from the couch too. The Weather app and the News app both get used a fair bit here.
Assign a button on your remote to the start key, and with up/down/left/right/enter/esc/backspace you can navigate through quite a bit of Metro without a mouse (though often you have to "intuit" what is selected, since there aren't consistent selection highlights, and those keys don't always work, and sometimes you'll get "stuck" and need to grab a mouse to hit an X or something).