One of the advantages that a Sorcerer has over a wizard is the ability to use and re-use spells when necessary. At, say, 10th level - how many dispel magics does a wizard have prepared? He has probably got between 4-6 3rd level slots, but how many of those are filled with dispel magic - probably 1, maybe 2. He could have a wand, but it is probably at a lower caster level if he does.
The 10th level sorcerer could potentially cast his dispel magic 20 times if he really, really needed to try to get rid of that high level magic obstacle.
Similarly with fly - the wizard might be able to fly, the sorcerer could make the whole party fly.
The sorcerer misses out on the ability to prepare esoteric spells for particular circumstances (I imagine that water breathing would rarely make it onto a sorcerer list) - but they can always buy scrolls for the spells that you very rarely need (but when you need them you *need* them).
It is interesting to note that unless the DM allows wizards to purchase scrolls and inscribe them into his spellbook, or find and make use of the spellbooks of defeated foes, the default wizard learns 2 spells per level; the default sorcerer learns 4 spells per 2 levels. So although the wizards have the -capability- to know more spells and have more spells available, there is a balancing cost involved*
In a campaign where DMs regularly allow wizards to expand their spell repertoire, but never ever make the wizards spellbook an 'issue' that might be stolen, damaged or destroyed, they are probably giving wizards a bit of an extra advantage (I imagine the core rules anticipate that there should be a danger to the wizards spell book - hence the existence of the 'Spell Mastery' feat (or whatever the feat is that allows you to prepare (int bonus) spells without having your spell book. I imagine that the feat rarely gets taken in most campaigns if most campaigns never have a threat to the spellbook!
I actually think that sorcerers are harder to create and run than wizards in many ways. Planning out which (of a limited range) of spells you want to have at each level, and then planning the order in which you want to acquire them and when it might be possible to swap out appropriately can be pretty tricky. You really don't want to make mistakes when planning your spells!
* I just worked this out. If the DM allows a PC to copy from an NPC wizards spellbook at the cost of spell level * 50gp, the cost for that spell repertoire would be 14,400gp. If the DM said that scrolls would have to be purchased instead, and assuming that we are not including extra-expensive ones, the cost for that spell repertoire would be 27,200gp. Presumably an equivalent PC sorcerer would have that much extra value in magic equipment?
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