If the they're part of an army focused on Nurgle instead of a generic chaos army? They can yeah. Between lore of Nurgle and the fact that taking out the tougher Chaos Warriors with Nurgle's blessings, the Strength 4 AP could be much more important then twice the number of S3 archers. This is especially true if you realize that it's not really twice the number due to the other allied armies present.Do you want to say that two archer units will do less damage than one Handgunner unit against Nurglites?
Really?