I was reading through the magic section of Dungeon Fantasy and prepping for a game, and the system feels less detailed than Pathfinder's (on max settings, full components, acquisition, and study). There are no spell components and spells are all cast the same way, dependent on skill level with gestures or words. As you improve, the mana cost, required words and motions, and time to cast (except for bards) go down. It feels very much like a superpower system, with casters having an energy reserve pool, then mana costs going to fatigue, and then hit points as resources run out.
If you like the Pathfinder 1e Vancian magic with the detailed rituals, components, and spell acquisition - stick with that system. Magic does feel more "magical" when you have all your settings turned up and casting is difficult again.
This system is better than "cheating" at Pathfinder 1e and ignoring components since it drops Vancian tropes and just makes spells a power list to pull from. If you are not into that detailed game and just want to "cast a spell" like a superpower, this system feels better since you are not fooling with daily memorization, spell limits, and that problem of having the right spell in your spellbook but you did not memorize it today. I know, scribe scrolls and keep them handy, and in a max-setting Pathfinder 1e game that is what I would do in downtime, burn gold and time and create a cache of one-shot scrolls to pull out and use when I really need that extra fireball spell.
Here, this works like a simplified "magic powers" style system with a few steps less complexity on tracking and memorization. GURPS has complexity in the personal combat area, so every game has that complexity budget and some things need to have less detail than others to keep them playable.
vs. GURPS Magic
GURPS Magic (and you can put the Magic expansion Thaumatology in here as well) is the sort of "superhero magic" of the main GURPS system and it also includes a bunch of spells that would be grossly abusable in a Dungeon Fantasy game (I turn into a dinosaur!). Dungeon Fantasy also makes tweaks to spells to balance them better and improve their function for a more dungeon-oriented game.
This is sort of the difference between this game and something like Fantasy Hero (Hero System), where you are using the base game's full power set to create fantasy spells, with balance and flavor be damned. Sometimes that is fun, but I can see how in a dungeon-crawling genre and setting you do not want your mages taking over the game and becoming gods. This happened to us in AD&D 2e and it killed our Forgotten Realms campaign. I see GURPS Magic as like Doctor Strange magic, sort of superhero style do anything spells that let wizards stand toe-to-toe with superheroes and others using the main rules plus expansions. Dungeon Fantasy is more the "D&D mod" for GURPS, with everything carefully gone over and made fun and balanced for party play.
If you want complex magic with components, symbols, and all sorts of other different styles of casting, use GURPS Magic with Thaumatology, and this will get you back to max-settings Pathfinder 1e. I am sure if you tweaked things enough you could use Thaumatology with Dungeon Fantasy, using the latter's spell lists and avoiding the unbalanced spells for Magic.
Dungeon Fantasy Magic: More Common
With power pools and the style of casting in Dungeon Fantasy, it feels more like a higher-magic world than a max-settings Pathfinder 1e game. To balance this, make casters way less common in the world, reduce the number of spellcasting NPCs, and let the players and only the VIP NPCs be the spellcasters.
One cleric in a village temple is a very powerful thing, and I would make most of the temple attendants non-magical followers and devotees. In Pathfinder 1e you can get away with a level 1 NPC cleric in every town and temple, and things still won't get terribly crazy since one light healing spell or otherwise a day does not make too much of an impact.
A 250-point Dungeon Fantasy cleric in every town and temple? No, these are clearly hero classes. If you want to do that, use the Delvers to Grow book and do 62-point clerics with 6-7 basic cleric spells and a 1-point power pool (so they are burning fatigue quick). Still, that is more like a level 3 Pathfinder 1e character, so make those relatively rare as well. A full 250-point Dungeon Fantasy character feels like a sweet-spot level 7-9 Pathfinder hero and has room to grow.
But overall, characters have way more powers in Dungeon Fantasy (even at the Delvers to Grow levels) and can use them in a lot more situations more readily. Casters are way more capable here.
The Spell Game
The magic here is more "rulesy" than Pathfinder 1e magic. There are maintained spells, concentration spells, and a few modifiers for casting spells while other spells are still up. With Pathfinder there are way fewer rules around maintaining spells with ongoing effects, but here the more a caster keeps up, the harder it gets. The best comparison in a superpower system, but this also makes me feel like Dungeon Fantasy's spells are way more "anime-like" than their Pathfinder counterparts.
I say that because these spells feel way more like spells you would find in a Final Fantasy RPG or Skyrim, where you cast, mana comes off a pool, and the effect applies. There is a cost to maintain buffs (that reduces as you level and can be zero), and with each magic spell that you try to simultaneously maintain others get harder to cast. Also, like in Final Fantasy, you are not dealing with Vancian memorization, the spells you know are the ones you know, as they are trained, learned, and improved like skills.
Is it better? Depends on what you like, honestly. There are times I feel the Vancian magic system is overused and a bit too close to D&D. As an alternative magic system that simulates a more videogame-style system of magic this works well.