Disclaimer: The following is using the assumption that prepared spellcasters are the power level benchmark to aim for. It could also be valid to downgrade prepared spellcasters down to the level of spontaneous spellcasters, but I would rather try to elevate other classes.
Spontaneous casting seems very poor. A prepared spellcaster has to learn a spell only once to gain access to all versions of it. Conversely, a spontaneous caster has to learn the spell multiple times. Spontaneous Heightening covers only two spells known per day, short of incinerating higher-level class feats to gain extra Spontaneous Heightenings.
This does not bode well for spontaneous casters, especially bards, who have a disturbingly low amount of spells known. A 7th-level bard knowns four cantrips, two 1st-level spells, two 2nd-level spells, two 3rd-level spells, and one 4th-level spell. A 7th-level sorcerer knows five cantrips three 1st-level spells, three 2nd-level spells, three 3rd-level spells, and two 4th-level spells; and they cannot even cherry pick one spell at each level due to their bloodline imposing choices on them. When a bard or a sorcerer must learn different versions of a spell at different versions, and a sorcerer is supposed to be a dedicated spellcaster, that repertoire becomes pathetic. The bard's Esoteric Scholar and the sorcerer's "X" Evolution can help here, but those take class feats. Their skill monkey chassis and compositions might help, but their spellcasting is woefully constricted.
Conversely, by 4th-level, wizards are frolicking around with Quick Preparation, which makes it a breeze to have just the right spell on hand for noncombat situations. (In fairness, this is clearly a massive outlier; no other spellcaster has anything that can remotely compare with Quick Preparation.)
According to Mark Seifter, this was done because people were suffering decision paralysis with spontaneous casters, but I cannot help but think that it diminishes their flexibility by a massive degree.
I think it would be...
As I am understanding the rules the sorcerer gains their bloodline spell in addition to thier other spells known. So the should get 3+a bloodline spell known at each level eventually.
That said sorcerer's are hilariously outclassed by wizards as printed. With no undercasting/ and extremely limited heightening sorcerers just dont stack up to wizards.
Between Quick preparation and the univeralist's drain arcane focus, it seems to me that wizards will be the most flexible casters.
I am trying to keep and open mind and will be running fraternal twin elves in the play test. One a wizard, one a sorcerer. I just dont have high hopes for the sorcerer in the sibling rivalry competition.
They need to give sorcerers something to make them feel like the kings and queens of spontaneous casting. If full heightening and under casting are just too powerful maybe allow them to learn spells off any of the lists instead of just one. I dont know what the answer is but I dont think we are there yet.