This is what I perceive to be the main difference between Shabazz and DeAndre's decisions to stay/go pro:
Shabazz was the unquestioned heart and soul of the team this year. Not only was he the go-to option whenever the team was in trouble or needed him, he also made everyone around him that much better, DeAndre included. When Shabazz was off, the whole team seemed to follow suit.
I've always seen DeAndre as a better pro prospect than Boat, but it'd be very difficult to convince me that DeAndre would go incredibly beyond Boatright as a contributor to/leader of next year's team. Shabazz's rise was in part due to the perception that he was the leader of the Huskies, that they were his team. Granted, most media bigwigs and national fans vastly undersold the rest of the team, but it was that characterization that fed his legend. The 2014-15 Huskies would not have been DeAndre's team; maybe it's just the Kemba-Bazz lead guard archetype, but if that falls to any one person, it would have been (and still most likely will be) Boat. Make no mistake, a "dynamic duo" type pairing of the two of them would have been great for the team and make the likelihood of repeating quite a bit higher. But it would not bolster DeAndre's image à la Shabazz.