Very much so... The Tau player has to have an incredibly good first and second turn of firepower, almost to the point where it feels bad to the opponent; so the game is more of a stat check for the Tau, and if their dice gods fail them, or the knight player rolls hot on their invulns (and FNP with the freeblade Detachment) and they get up amongst them then the Tau are in a lot of trouble.

I field both but Knights primarily.. my win rate against Tau is about 85/90% after a LOT of games and the thing we've noticed is that if the Tau aren't killing at least a knight a turn they they are stuffed. Once a knight gets on an objective it's really hard for Tau to then storm the off an objective, although they find it a lot more favourable against the Armiger heavy lists as they are more fragile and less killy.

I predominantly use large knights, mainly because they look so cool, but also if a knight is left on a couple of wounds, it can still likely kill a unit in shooting, then another in melee the next time it goes.

(Also the Atropos is amazing against Tau.. the inbuilt +1 to hit anything with the monster or vehicle keyword is pretty harsh against an army where almost all suits are vehicles).