Well, there is a good variety of spells for one thing. Even among basic attack magic, they operate in different ways; fire shoots simple balls of fire, lightning strikes from above, etc. Higher level versions do more creative things, like conjure lightning whips to wield temporarily or conjure massive ice spikes that not only cause damage but serve as physical structures to block things or serve as footing. Of course, there are other spells as well, like stat buffs, healing magic, status ailments, weapon enchantments, etc.
Spells can be charged to different levels once unlocked, so you want to channel for as long as possible. But after you release the channeling, there is still a period where you are casting and can still be interrupted before the spell is actually fired off; so it can be risky to leave it to the last second.
There is also a system for combining the efforts of multiple people casting the same spell. A team of 4 sorcerors all casting the same spell can be incredibly powerful, literally turning the battlefield into an endless storm of deadly magic where nothing can even fight back. It's hard to pull off though, most pawns aren't trained properly for it.
The system for aiming spells is also quite good, you can choose both auto-aiming modes where you lock onto enemies (or parts of enemies, for larger foes) and ground based AoE targetting for better control in circumstances where you want to send a spell right between a group of enemies, for example.
Edit: Spells also consume stamina just like physical actions, and managing that stamina can be a big part of effective spellcasting. Though it gets rather gamey when it comes to using consumables to restore stamina, that aspect is honestly rather broken.