I consider the extra dice from Sneak Attack to be weapon dice because Sneak Attack only works with weapons, and the Sneak Attack damage does not have an explicit type, e.g. piercing, slashing, but inherits the type from the weapon used to make the attack.
Given Savage Attacker's once-per-turn limitation, and the interpretation that it does work with Sneak Attack dice, I refer to Savage Attacker as "the Rogue feat".
The increased accuracy from an ASI is strictly better than Savage Attacker. However if dexterity is at 20 and the Rogue wants to do more damage, then Savage Attacker is a good option. The expected damage increase on the 6d6 Sneak Attack dice of a level 12 Rogue is 2.37. The expected damage increase on 10d6 Sneak Attack dice is 3.05.