you being ignorant now. Avril for his career averages 8.4 sacks per 16 games. Williams for his career averages 10.4 sacks per 16 games. say what you want about it but that's a roughly 25% upgrade in productivity per 16 games just in terms of sacks not to mention Williams is a more complete DE with a much larger skill set!
listen, weather you want to acknowledge it or not Williams IS arguably the best 4-3 DE in the league, this is a FACT! He's so good that he made the move to OLB after his 5th season and instantly became one of the best 3-4 OLB's in the league. If he somehow became a free agent 4-3 teams would be lining up around the block for a chance top sign this dude.
Avril on the other hand is probably not even in the top 10 discussion for 4-3 DE's as he's a one trick pony speed rusher. yes he is good at his one trick but without playing along 2-3 other really good Dlinemen he would be neutralized in a lot of ways. Avril will get around 8 mill per and he should be plenty happy for that because if he was, oh I dunno, a Jacksonville Jaguar he would be basically Kalimba Edwards. . .