I'd go by the following order:
#1
#4
#3
#2
a 3 ball potential big man is pretty limited in his development. That's why #2 is last even though he's 18yo. On the other hand, a B potential 18yo will be better than an A potential 19yo if trained for an entire season, so #1 is first. #4 gets the nod over #3 because of the A versus A-.