1) For NLAW, the sensor has the visibility from the get go. For cannon fired missiles it is not the case. It comes out of the cannon at and gets homing sensors get the target location, only then it can reach the target.
2) Firing gun is faster than firing a missile. Missiles are mostly used for targets that are far away that the cannon gun projectile cannot reach accurately.
3) Only T-90 M fires on the move. Not T-90S, which is what Indian army has.
Russian losses in Ukraine have been mounting. These aren't small collaterals but signature pieces of Russian attack, denting the country's reputation.