It's really too bad that Bender wasn't able to play for Croatia last summer at Eurobasket. Prior to that tourney, every International competition, basketball camp, etc. where he played against older peers he excelled and appeared to have a massive upward trajectory. But unfortunately, because of Adidas vs. Nike politics and limited playing time on his new pro team we have very limited film on him from the last year.
For me Sabonis seems to top out at fringe NBA starter. Bender, on the other hand, because of his unique physical profile (size combined with agile movement) seems like he could be something special if the cards are played right. For that reason, I'd be willing to risk him being a total bust and draft him at #3.
I also don't quite know why these two are being compared to each other since they fall at significantly different parts of the draft. The Celtics could easily select both if they wanted.