Honestly, you are talking out of your ass on a lot of this and clearly don't even know what you are talking about.

"If he's so good why isn't he making top dollar?"

Because he is on his rookie contract.

"So Raji played out of position for a few years."

Raji has arguably played out of his position his entire career. He isn't a true NT nor is he a DE. He is a pass rushing DT, a position we virtually never play him in.

"And 6.5 sacks as a 3-4 DE is pretty dang good."

He got those 6.5 sacks as a NT in 2010, five years ago. Since that time he had 3 sacks in 2011 at NT, 0 sacks in 2012 at DE, and 0 sacks in 2013 at DE. You should in theory produce more sacks at DE, while providing more run stuffing ability at NT. He hasn't fulfilled either of those criteria.

"His pass rush is existent."

Existent does not mean good. Again though, at NT you want run stopping ability and the ability to two gap. Raji can barely do those things. Williams excels at those things.

"Lining up as a DT is equivalent to lining up as a NT."

Technically a NT is a type of DT. However, when it comes to responsibilities and play styles they are completely different entities.

0-Tech and 1-Tech are NTs, 3-Tech is a DT.

0/1-Tech need to command double teams, 3-Tech does not.

"You are using it against Raji that he played more snaps?"

Because you are using volume stats, Raji will look better.

"Williams couldn't hold up for as many snaps as Raji played."

Or the coaching staff/players around him allowed for Williams to be a two down player and it had nothing to do with ability.

"It's understandable that his efficiency went down for how much he played."

So, you are saying Raji isn't as good anymore? Because that is true.

Pretty easy counter argument laid out as well. Williams has less snaps on him so bringing him in he might be fresher and more ready to play then Raji.