Reasons for new gems to join Bloodstone's side:
1: He knows about their past.
2: The gems know as little about him as they do Aqua
3: His invasion is what allowed them to be born
4: If Aqua, Rose, and co. had succeeded earlier, none of them would exist
5: Aqua is a traitor to gem kind, favoring humans over the gems. How do the new ones know she won't make this decision again when it's between humans or them?
6: The new gems have done nothing wrong in his eyes, if they switch he would be willing to grant citizenship to them on Home-World
7: Blood has all of gem kind backing him

Reasons to stay with Aqua:
1: She's nice and hasn't tried to destroy the new ones yet
2: She taught them how to use their powers
3: She was the first gem they met
4: She hasn't fired giant lasers at them

- The question remains though, who will consider switching sides if given the opportunity