Nerlens Noel and Anthony Davis actually have very similar body types. Noel has an inch on Davis (6'11'' to 6'10''), but Davis has a slight weight advantage (220 pounds to 215).
They are also both known for their incredible length. Davis has a 7'4'' wingspan, narrowly edging Noel's 7'3''.
There is one major difference, though. Davis was a guard growing up and didn't become a big man until a massive growth spurt in high school took him from 6'3'' to 6'10''.
Athletically they are both stellar. Both have exceptional leaping ability and are very agile for their size. They fly up and down the floor and are always a handful for opponents based on pure athleticism alone.
While that spurt turned him into the star he is today, it has also limited Davis' ability to add muscle. His body can't support it. This is the same reason Kevin Durant is still one the NBA's skinniest players.
It won't be a major con for him as Davis is so talented in every other facet of the game, but it may present problems against stronger players.
Noel on the other hand, is a big man born and raised. While he's still fairly skinny now, he has the frame to add more muscle. Ideally, his playing weight should be around 240 pounds, and he has plenty of time to add it.
By the way, we have to talk about their hair. Davis is known for his now trademarked unibrow. Noel has a classic high top fade. What is it with Kentucky big men and ridiculous hair cuts? Noel looks like Gerald from Hey Arnold.
John Calipari has to do something about this. I'm not saying he should enforce some sort of Yankees-esque facial hair ban, but he should prevent cartoon haircuts.