Garmont T8 NFS vs. Belleville One Xero vs. other modern combat boots. Best boots for performance, support for heavy rucks, and durability?

I personally use Belleville Mini-Mils for everything except cold weather operations. The best boot is highly subjective. Both of the boots you mentioned are excellent, I would probably go with the One Xeros over the Garmonts.

I used T8NFS through bolc, ranger, ABN operations, and day-to-day wear. Love them, they come broken in pretty much out the box. Only downside is they take a good while to dry, and the laces that come with them get caught on everything in the wood line.

I love the Garmonts. I think I put over 1000 miles on my pair before the shoe laces snapped and I decided it was just time to replace them. I switched to Danners though, and Danners have been the most comfortable out of the box boot i've worn so far. I've had them for about a month now and they're still insanely comfortable and form fitting to my feet.