Simmons is basically Ball minus the shooting and defense but plus 4 inches. I'd take Fultz and Ball over Simmons.
Simmons has a lot of talent, but I think he lacks the right mindset to succeed. He doesn't work on his game. I read reports about how his coaches in Australia didn't like his work ethic. One report said he was a better shooter when he was younger but didn't work on it, so he got worse.
Simmons is special but he didn't play defense in Australia. He didn't play defense in AAU. He didn't play defense in college. He didn't play defense in summer league. He has no 3 point shot which isn't horrible for a PF but he has no midrange game either. Also, as good as he is in the paint, he struggles against size and athleticism. Jaylen Brown out played him head to head in HS and in summer league.
Fultz can score from everywhere on the court. He can score though double and even triple teams. He can pass a lot better than his highlights show. If you watch the game you can see great passed that his teammates blow with bad misses. He is super athletic and has great size for a PG and good size for a SG. Really the onlthing that can stop Fultz from bring a star is Fultz.