#1 Pro - He'll have more familiarity with talent before they move to the main roster

As I previously mentioned, part of the reason why so few call-ups from NXT have found success on the main roster is because of McMahon's perception of them. If Mr. McMahon didn't view them in the same light in which they prospered in NXT, then he'd change things around to make them fit into his vision.
Part of the reason for those changes was because Vince didn't pay a great deal of attention to the NXT product. While that might seem crazy to us fans, it makes plenty of sense. He's a billionaire who is probably pretty darn busy all the time. He's already pouring a ton of his attention to the product in order to make things go smoothly for RAW, SmackDown and PPVs.
Earlier this year, he asked for Triple H to bring up the four top guys from NXT to RAW and SmackDown. He didn't know the stars himself, so his son-in-law was forced to take Ricochet, Aleister Black, Johnny Gargano, and Tomasso Ciampa out of NXT and onto the flagship shows.
By putting more of his focus onto the yellow brand, he'll already have a good working knowledge of stars and their strengths and weaknesses. The transitions to the main roster will hopefully be smoother and less clunky like some (EC3, Kairi Sane, Viking Raiders) have been this year. He's also given a lot of control over RAW and SmackDown to Paul Heyman and Eric Bischoff so it's not like those shows are losing out on having experienced hands behind the scenes.