Low to mid level, team wise, little to no IOs: Both are similar, although it might depend on the controller's secondary. At this level, most people see both ATs as CC functioning classes.
High level, no permadom but decent IOs: This is really team dependent. If you team with a bunch of IO'd people, then the CC from either archetype makes little difference. If you choose to team with not-so-max'd out people, then both ATs still function pretty similarly in terms of CC, dominators focusing more on damage and controllers focusing more on support (obviously)
High level, max'd out, dominators with permadom: Dominators become the ultimate CC archetype. Once again, team dependent because the amount of CC actually needed will vary on whether enemy groups burst like a bubble (control powers take a backseat). A single permadom can usually cover an entire team's need for crowd control, possibly making controllers' and other dominators' primary powers redundant. Controllers either become team carriers or (unfortunately) situationally useful.
Note that illusion is kind of an exception. Although perma-PA is a bit slow to keep up for an every-mob control skill, it is the only reliable way to solo "control" most AVs permanently if we don't count Mind or Dark permadoms spamming their single target confuse skill. This becomes really useful when you're in a TF and no one is able to tank an AV, which has happened to me on my illusion controller in Ms. Liberty TF (tanking Lord Recluse) and Imperious TF (tanking Romulus)