Answer this honestly; you would rather have Swanigan on our team than Kuzma?
To your points, Kuzma is averaging nearly 5 rebounds a game and was a good rebounder in college. Don't agree that he doesn't rebound. He's better at it than Harkless. As for defense, he's a rookie, and I don't see anything about his profile that suggests a long term issue.
For me, it's easy. Kuzma would immediately be a starter. Swanigan is most likely going to be a backup while he's in Portland. Don't see him ahead of Collins long term. I like him, he'll be a good role player, but come on. We need a Kuzma a lot more than we need a Swanigan.