Shatter is a better damaging spell than Snowball Swarm, but it's also significantly louder and more destructive. Even Fireball only damages flammable objects. While Snowball Swarm might alert the next room, Shatter stands a good chance of alerting the whole dungeon, if not the next dungeon over, too.
Overall, I'm mostly disappointed that nearly every spell in the companion is from the Conjuration, Evocation, and Transmutation schools. Most spells were already from those schools, and this didn't correct that. I would've liked to see more Abjuration, Divination, Enchantment, and Illusion spells. Others are probably disappointed by the lack of Necromancy spells, but I've never cared for that school; the effects tend to be too narrow, with some exceptions (Eyebite). As it is, though, there are still no 5th level Necromancy spells for Wizard, which seems kind of weird.