A man can only be so well trained before he reaches peak power. A smart bullet, that is a weapon that can guide itself based on what it senses, what it is programmed to do, and any other variable has far more potential then correcting a bad shot. Concealment is slightly mitigated, as the bullet can hit the target without the person actually seeing them. The bullet could also be fired into the sky, and have it steered into the enemy position With ease. This can also be more effective with explosives, as the weapon could be taught to fly over enemy cover and detonate where the enemy is flanked or exposed.
It could also be combined with materials that could change themselves on the spot to deal more damage. It could harden before impact on bone/ splinter when in the face of delicate organs, and again, correct a bad shot. ((assuming we can make the bullet "smart" enough to do that kind of thing.)
Also, Training our men is not exclusive to smart munitions. Even the most accurate sniper or other personnel can miss. The skill of the soldier is also put into question, and it puts a higher skill ceiling as the soldier has control over the weapon in all situations. In later eras of technology, A soldier could theoretically steer the bullet, even after it leaves it's origin by communicating to the bullet while it is in the air.
The first iteration would probably just be a round with a set of programmable fins. The soldier would put in commands, and the bullet/grenade would follow those commands as best as it could, while also using its own systems to steer better into its designated target ( Painted Laser? IFF Sig? Thermal detection? Something along those lines.)