Why no multiple choice. I want Powers + Vancian.
Examples for Wizard Spells
The Lesser Form of a spell can be invoked as long as the spell is prepared.
The Greater Form is more limited, the caster usually has to take a short rest to cast either the lesser or the greater form again.
The True Form can be only cast once per day, as it releases the majority of the pattern, and it requires an extended rest of the caster to eradicate the last traces - and he must do so even if he wants to prepare the spell again. Still the remains of the pattern can be sorted and brought into form, but this requires a short rest. If done so, the caster can use the Lesser and Greater Forms again, even though the True Form will remain unavailable to him.
Notes:
The spells are basically "balanced" as they probably would or could be in 4E. The rule saying that you cannot use a greater or true form of the spell after you've used the greater form, and not use the Lesser and Greater Form after you#ve used makes the Wizard magic "more complicated" - you have to decide early on in any given engagement whether you want to use the Daily version of the spell or not - and you may find yourself entirely out of magical spells after you've cast all of your True Forms. To compensate, the True Forms of the spell are stronger, though, than "normal" 4E dailies would be.