Go back in this thread and read their scouting reports, their games are very similar and they are the same height with a huge wingspan, differences are that BB is stronger and Evans hops. They have tons in common, but the point of thread was they are both projects with huge upside, so the jazz shouldn't have two of those type of players on the roster.
Why? Evans is a SF. He'll never be a power player, nor will he ever play the 5. Biyombo is a 4-5. There are 12-15 roster spots. Generally teams have 8-9 as rotation players. The rest are projects, fill-ins, washed-up vets or injury-insurance.
I guess if we have too many "projects" then the answer is to also trade Favors and Hayward for players like Bell and Fisher.
The Jazz weakness under Sloan is that they haven't had enough "projects." Either Sloan or KOC (depending on who has the ultimate authority on roster decisions) has looked for old veterans to backfill the roster instead of guys that still have some upside. Every year I watch exciting "no-names" emerge with other teams while teh Jazz roll out players like Elson, Bell, Knight, Hart, etc. Yes, there is the occasional Millsap or Matthews. More often, though, is the re-signing of a Collins or bringing back an Ostertag or Eisley.
I'm not saying the Jazz should have 15 "projects." A team needs veterans. But make sure those veterans are key contributors. Otherwise, go with projects for the last 5-6 roster spots. And if a couple emerge, then that gives you flexibility to trade them or the starter(s) in front of them to upgrade other spots.
You take BPA (and that "P" might mean player or prospect). If you worry about who else is in front then you end up passing on Stockton because you already have a Ricky Green.