4-3 vs. 3-4

Factual Questions
1

As far as football defenses go, is one superior to the other? What are the situations where one would be appropriate over the other? Also, why does the 4-3 seem to be so prevalent?

2

Here’s a nice thumbnail description of the 3-4 and 4-3

http://guides.ign.com/guides/479093/page_5.html