I don't think it should be a straight comparison with Neal. Penney is not just a spot up shooter. He is extremely good at getting shots using screens in set plays. He is more of a poor man's Richard Hamilton. He could provide the second unit a unique scoring option.
He might not have the quickest feet on the defensive end, but he is strong and is smart.
Abercrombie lacks the explosiveness needed to get by as a pure athlete, he can jump but it is a slow jump. He would also need to bulk up to be a 3 in the NBA. His jump shot is streaky as well.