In a 4-3 you know exactly who you've got, you've got one man...

In a 4-3 you know exactly who you've got, you've got one man and you're going to be basically blocking him. In a 3-4 you could have the tackle some time, you could get a linebacker some time or a defensive end who is standing. They'll throw a lot more looks and a lot more mixes at you in a 3-4.