There are several Crowd Control options.
The strongest one, particularly vs mobs, would be a Conjuration focused mage (wizard or sorceror).
Grease, Glitterdust, Pitt line of spells, Web (use Featherstep/Freedom), Stinking Cloud (use Delay Poison Communal!) mass disable enemies (or make them suck like Glitterdust).
Later Chains of Light neutralize bosses with poor Reflexes (Vine Trap and Icy Prison also work).
That sounds great. Is there much of a decision to be made between Wizard/Sorcerer or would it be more of a cosmetic choice?
It is definitely not a cosmetic choice.
A Wizard can be seen as the standard for arcane spellcasting. They get the fastest spell access, they use intelligence as their casting stat and they can learn every spell in the book. They prepare a number of spells per day in a limited number of slots.
In theory, the Sorcerer is one level of spell access behind the wizard and limits the number of spells he knows in exchange for a greater number of spell casts per day. Instead of preparing spells from a number of slots, they have mana points they spend for spells.
In practice, the Wizard is likely to specialize in 2 or 3 schools of magic and magic as a whole is much more limited in a CRPG than in PnP. So its not like they are going to always make full use of their spellbooks. The Sorcerer's advantage in firepower also diminishes at odd levels -- the wizard got to a new level of magic and the sorcerer didn't, thats 3 casts for a specialist wizard. Further, there's the Thassilonian Specialist, who sacrifices 2 schools of magic in exchange for getting as much firepower as a Sorcerer. That drawback of losing entire schools isn't too much of an issue if you're, say, a conjuration specialist since conjuration by itself can do anything.
So in truth, if you take say, a level 1 Sorcerer and a level 1 Wizard -- both specialized in Conjuration -- you might see that the Wizard has 2 or 3 casts of Grease memorized for crowd control and a fourth spell (if thassilonian) that is up in the air. Perhaps Sleep. The Sorcerer gets to cast Grease as many times as he wants out of 4, as well as the second spell he learned, whichever he chooses.
The major difference is that the Sorcerer is more tactically versatile than the wizard. If, in the course of a whole adventure, the Wizard needs one more cast of his favorite spell, he's doomed. The Sorcerer on the other hand, spends his power accordingly to his need.
This is without counting on things like school powers and bloodline powers, but those are more specific to what sort of character you want to build.
PS: sylvan sorcerer is the best character in the game, you get an animal companion and you can definitely specialize in crowd control.