I don't understand why there is any statistical debate on who the better player is. Less intelligent individuals are comparing the total stats of Kante to Herrera, when Kante has played 688 more minutes of football (+7.6 games) than Herrera. Not a very smart thing to do. Per 90 statistics tell you Herrera is better all around midfielder than Kante.
Attack per 90: Herrera creates 1.42 chances, 1.21 key passes, and scores 0.04 goals. Kante creates 0.58 chances, 0.55 key passes, and scores 0.03 goals. -> Herrera is the clear winner
Possession per 90: Kante is at 89% passing, and Herrera is at 88%. But Herrera wins 47% of his duels where Kante only wins 40% -> Close, but slight advantage to Herrera as he wins 27% more aerial duels.
Defense per 90: Herrera wins 2.45 tackles, 3.66 interceptions, 0.26 blocks, and 2.45 clearances. Kante wins 2.33 tackles, 2.40 interceptions, 0.13 blocks, and 1.43 clearances. -> Shockingly Herrera emerges as the clear winner.
Stats aside, if you watch Kante, its clear he's consistently better at the defensive aspect of the B2B midfield role than Herrera. Note Herrera isn't a pure B2B. He's being deployed as a ball winning midfielder who in possession plays more like a deep lying play-maker. Despite the more conservative restriction on when he can move up the field, Herrera manages to impact more aspects of the game (attack, possession, defense). Which makes him a better player in my opinion.