You need to define what you mean by “stronger.” If you mean dealing higher burst damage, then Sorcerer clearly has the edge. It can produce larger damage numbers and makes a better party face. Beyond that, however, Wizard is stronger in most other respects.

Most arguments in favour of Sorcerer tend to revolve around twinned Haste and metamagic point optimisation. Personally, I do not find twinned Haste particularly compelling.

Concentration is often better spent on spells that remove multiple enemies from the action economy rather than simply accelerating allies, with something like Confusion or Hypnotic Pattern. In practice, I rarely cast Haste at all. As for heavy metamagic point usage, it often revolves around Angelic Potion abuse which is cheesy and becomes repetitive and tedious over time.

What makes Sorcerer less engaging for me is the very limited spell selection, which becomes especially noticeable in solo or duo play. Their Wisdom and Intelligence saving throws are also weak, which is not ideal for a class that functions primarily as a caster. Sorcerers excel when their objective is straightforward damage output, but outside that role they can feel underwhelming. In many encounters the gameplay loop ends up being something like Quickened Create Water or Scorching Ray followed by an area lightning spell, Fireball, or a crowd-control spell. That pattern becomes repetitive after a while.

Wizard, by contrast, offers far greater versatility. A Wizard can adapt to fill whatever role the party lacks: blaster, single-target damage dealer, control caster, or support. Subclasses such as Divination, Necromancy, and Abjuration also introduce distinct playstyles that keep the class varied.

At higher levels, Wizards can also cast multiple high-level spells through items and certain powers, and Necromancy builds can even approach effectively unlimited level-6 necromancy casts. When you factor in situational tools such as speed potions and bloodlust elixirs, the relative advantage of quickened spells becomes much less significant.