The biggest difference is that the K&N kit's inlet tubing and heat shield is made entirely out of fairly basic plastic, while the aFe Stage 2 Kit uses aluminum tubing and heat shield, both of which of have black wrinkle powder coat finishes. That specific aFe kit also has a dry filter design that's easier to clean and maintenance than the K&N's oiled filter. Whether it's worth the money depends on what you're looking for. If you just want some extra power without much fuss, then the K&N's you're better bet. If you want something that's stronger, looks a little more aggressive under the hood, and is easier to deal with, then the aFe kit is your better bet.