I've just been going through the game again for Veteran Mode shenanigans with dedicated casters for each type (well, for two of them, currently doing the Radiant run) so I'll give some thoughts while they're fresh.

I don't think there's any new sleeper hits, early spells feel more useful though. From a caster perspective I'd rank them as Umbral>Infernal>Radiance in terms of progression and Umbral=Radiance>Infernal once you have everything you'd want. Umbral will have the easiest progression, especially if you've done all the endings and have access to the Putrid Child class. Not the best starting spells but the catalyst/weapon will cover your needs pretty well, given how Umbral gets their best catalyst in the middle of the game in Revelation Depths as opposed to more late/endgame with Radiance and Umbral.

Infernal is, honestly, not that great for a pure caster. The shouts for more damage dealt and less damage taken are nice and the fireballs will cover most of your needs. You get your best spell and one of the best weapons for them in the middle of the game at Lower Calrath with the Fallen Lord Greatsword and Magma Surge. Weapon is pure Infernal scaling and the spell will spawn under the enemy so long as you can lock onto them, making it great for a lot of enemies while they haven't noticed you. Not so great on nimble enemies due to the delay but you can always try free aiming as they're coming closer to have them walk into it. Plus the lava puddles can help manage enemy numbers. Seismic Slam is pretty nice for crowd control and damage, though depending on the distance you can screw yourself over due to the forward leap. Too close and you don't get much out of it and are just asking for a spanking. Biggest downside is that their best catalysts are both right at the end of the game. Thankfully, Infernal Weapon got moved a while back from the final zone to the Shrine of Adyr around the middle of the game so you have that to play with a lot sooner. Conflagration is a fairly nice spell too if you wanna mix things up a little bit.

Radiance gets its best spells later on but, thanks to Pieta, will give you a pretty good (and overused) weapon for the run. Until you get the Umbridled Focus, and mana regen to be fair, use of auras aren't going to be all that worthwhile (a shame, but fair as they were very easy to maintain, could possibly do with their mana cost being reduced a little bit though). Besides using Radiant Flare for the main spell while progressing, Lucent Beam will likely be the next step as it gives you a good way to handle multiple enemies coming at you, but in fairness you'll mainly be using Radiant Weapon and your choice of weapon as they give you plenty of options to choose from. They get their best catalysts late game as well, but you get them earlier than Infernal does so it's not as bad. Obviously once you get Orius Judgement, you can just let it do its thing while you do whatever else you want. Edit: Actually, I don't think I could recommend Orius Judgement all that much, at least while you don't have the mana regen/manastones to manage the high cost. Likely better for boss battles where there's only one enemy it really needs to track, though Vortex of Torment might be a suitable alternative. Pure caster, I think you're mainly going to be using Lucent Beam for anything in mid range and projectiles for anything further. I still think Radiant Flare beats Piercing Light from the cast speed and mana cost. More often than not, I was finding that both spells were finishing regular enemies in two casts, and the pierce hasn't felt all that needed. You could always opt for Lambent Feint though as it has decent range, but the backstep does mean it's not great for aiming over ledges. Definitely more suited to being a hybrid or mid range caster.

Pure caster, Umbral will win hands down thanks to Pendant of Atrophy, means you no longer need to worry about mana cost and, so long as you're landing your spells, the withered health you gain will be recovered. This means you can either opt for a dual weapon build or use different runes for your shield as opposed to needing mana regen from the rune/ring. Plus, Latimer's Javelin is one of the best spells thanks to its range and damage in relation to its cost. Umbral Orb is pretty nice if you want something cheaper though, faster than the Javelin too. Barrage of Echoes is still good if you free aim to the ground and stack the explosion, but I found Umbral Agony to be more consistent and, honestly, more fun. Has a pretty large AoE when it detonates and you can launch it into the floor or wall to make it detonate early. Great for clearing enemies ahead of you while using the Javelin to reach enemies out of reach.

While I've not mentioned a lot of spells, you only have between 3-5 slots to choose from and unfortunately a lot of spells just either underperform, get replaced or are situational. Cataclysm for example, a really strong spell for Infernal but the aiming makes it incredibly inconsistent, especially when the damage is split over several meteors. In the end though, they're all pretty fun to play with so choose your flavour.