I think that we take the best nose tackle available, regardless of opinions about 3-4/4-3 defenses. We have a pretty solid NT in Kyle Williams. He can handle his job there better than people think. He was all ready taking up a lot of double teams last year because he couldn't be stopped one on one. In a 3-4 will he get tired? Yes, but that does not mean that we have to draft a 3-4 nose tackle. Another Kyle Williams would be awesome. They could spell each other and on every down they could also be a pass rush threat.
Think about it. If we get a Big nose tackle and he plays on running plays and Kyle on passing, how quickly do you think the offenses will pick up on that. No way should we go after a huge 3-4 nose. We can play the 3-4 just fine with Kyle, but it would be wise to get another guy just like him in there.
Besides, LT is a more pressing need.