Thought I would share DS's take on the three boots ordered: Danner Rivot, Danner Tachyon, and the Belleville C320 One Xero (Wearing Darn Tough midweight Tactical boot sock)
Danner Rivot STF
Size 11 EE
Certification: AFI 36-2903 Compliant, AR 670-1 Compliant
Pros: Beefy sole, the most well-made boot (boot's upper is stitched to the sole and there's cushioning on the tongue and collar), very comfortable in the ankle, longevity: this boot will last
Cons: This boot will survive at the expense of the man/woman wearing it - very heavy when dry, comfort in the wrong place (collar cushioning), less support in ankle than Belleville, pricey at $400
Danner Tachyon
Size 11 EE
Certification: AR 670-1 Compliant (The only certification listed on the box - I have found seller websites that state this boot is AFI 36-2903 compliant)
Pros: Immediately loved the feel of this boot, very Light, feels like a running shoe, immediately comfortable, thin sole, great boot for heat
Cons: Construction: glue and gaping visible between sole and upper, no ankle support, perhaps not the best cold weather boot, noisy - the sole squeaks on hard floors
Belleville C320 One Zero
Size 10.5 Wide
Certification: AFI 36-2903 Compliant, AR 670-1 Compliant
Pros: Nice ankle support, a mid-weight boot at 40 oz/pair, Beefy Sole, Under $200 but construction is better quality than Tachyon
Cons: would benefit from an insole (cushion), heavier than Tachyons,
So far, DS says the Tachyons were the most comfortable boot. However, he isn't happy with the lack of ankle support. So, the Belleville wins this round.