"I think it's fair to say that Solo specializes in understanding people; Illya understands things."

This hits the nail on the head. To use another iconic TV team to illustrate, Spock and Kirk are very similar. Spock's logic and Kirk's intuition make them unbeatable, also. They complement each other; neither one would be as successful on his own.

It would be way too easy to say the intuitive half of the team is weaker, but it simply is not true. Some may think that though Napoleon is not dumb, he IS dumb compared to his partner. Also not true. They are different, but equally intelligent.