One more thing- pairing is an active process, in the moment, while code review is reflective. During coding, you are exercising a lot of "instinctive" skills, and in a pairing environment, you are pressured to act.

Code review happens after the fact, and gives the developer and the team a chance to reflect on what was done and to use deeper, slower skills.

I'm well aware that our Twitter-fueled society is trying to eliminate reflection as a practice, but thoughtful reflection is a tremendous source of learning and growth. Removing reflection from the coding process limits the growth capabilities of the team.