A big part of it is NXT can slowplay a lot of storylines like the whole SZ rise to the title. Everything on WWE tv is about ratings that week and if they aren't working they scrap a storyline.

The other biggest part imo is that NXT doesn't have any 1 guy the show is about. Every Raw has the same formula, Authority sets up evil thing that main hero has to overcome, show is built around talking about the hero overcoming it and then at the end the hero overcomes it or doesnt because Authority cheats even more. They spend almost 3 entire hours just building what Cena (or whoever) will be doing that night.

In NXT the champ gets as much time as the opener (longer matches but you know what I mean), it is a group effort to make a great show top to bottom just like WWE used to do. Every segment is important and they focus on each segment. It makes every story intriguing rather than every story just being time filler before Cena comes back.