Pro: Trading for LaVine could also get John Collins off payroll
When the Jazz acquired Collins, the reasoning was solid. He was a productive big who could be had for pretty much nothing. Sadly though, Collins disappointed with the Jazz, and they have him on their payroll for two more seasons.
If the Jazz want LaVine, they could knock out two birds with one stone by getting rid of Collins in the process, who could be used to help match salaries. There have already been proposed trade pitches for Collins. If they can get him off the team for a star like LaVine without sacrificing any assets, that's a home run.
LaVine is paid more than Collins, and his impact when it comes to winning is questionable, but at least he'd give them more bang for their buck than Collins would. However, no Collins would also unclog the Jazz' frontcourt.