So I just read the rules of sop, and it seems functionally identical to vancian casting. Am I missing something? Does the difference not become apparent until you read each sphere?
It really isn't. Let's just take a very simple example: the ability to teleport.
Under vancian casting, it's a bunch of different spells, and learning one is completely unrelated to the other. You can learn and cast Teleport without knowing Dimension Door, or a swift-action short-range teleport, or any other teleportation-effect. It's just suddenly a whole new type of magic you can do once you hit 5th-level spell slots.
With Spheres, you'd learn the
Warp sphere. This gives you a teleportation-effect right at level 1 if you like. Sure, it's only close range, only one creature, requires line of sight, and requires a standard action - but you can also do it whenever you want, all day long. And with a spell point, you can push it to medium range. And you can build on that!
With another talent, it's up to long range. With another, you can teleport multiple creatures. With another, you no longer need to touch the targets. With another, you no longer need line of sight. And you can also learn to teleport objects or unwilling creatures, or to use it offensively in other ways.
So that's right there is your first difference: With Spheres of Power, you can gradually build up proficiency in a concept, instead of it being all or nothing.
But the second difference is also important: You don't build a fixed spell out of those talents, and then only use that!
The Warp sphere is maybe not the best to demonstrate this, with it's limited amount of talents. Take a look at the
Destruction sphere instead, and suppose I go with a thunder&lightning theme.
Sure, I can make a "chain lighting" effect by combining Chain Blast (Blast Shape) with the Electric Blast (Blast Type). But with the right talents, I can also instead shape that into a wall with Energy Wall, create a burst with Explosive Orb, surround myself with a deadly aura with Energy Aura, or many many more - in addition to just the standard ranged touch attack, of course.
But I can also spontaneously decide that I'd rather than having an easier time hitting enemies wearing metal armor, I'd rather do a bit less damage and have a chance to daze them and use the Shock Blast (Blast Type) instead. Or I can go with the Reverbating Blast (Blast Type) and apply a huge penalty to concentration, and do sonic damage. And if I have the Admixture talent, I can even apply two Blast types at once!
Suppose I end up spending eight talents on the Destruction-sphere (Admixture, Greater Blast, Chain Blast, Energy Nova, Energy Wall, Electric Blast, Shock Blast, Reverbating Blast) - a full caster would get 3 talents every 2 levels (and start out with a bunch), for comparison. A dedicated blaster would take Greater Blast once more per 5 caster levels. How many spells do I effectively wind up with? Not counting the different damage levels possible?
Destructive Blast, Electic Blast, Shock Blast, Reverbating Blast, Eletric/Shock Blast, Eletric/Reverbating Blast, Shock/Reverbating Blast - that'd be seven spells, and then the same again for every different shape, for a total of 28 different options at any given time. And adding more shapes or blast types is easy, it just takes a talent.
Now before that seems too intimidating - most of those will be for specific situations. No need to impede the concentration-checks of non-casters. No need to disarm a dragon. Switch damage types depending on enemy. Some of the admixture-combos are so good you'll always use them (because admixture is free within the same elemental group), some will be rarely or never used.
So Spheres of Power can be
a lot more versatile than anything you get from Vancian casting. Trying to do anything like the above with a Vancian caster would be pretty challenging, and for some things outright impossible (sure you can maybe get a dazing electric wall, but one that disarms?)
