As much as I've been critical of Smart over the, I'm actually going to say Smart in this poll.
In the past I was never a fan of starting Smart, but that was due to the makeup of our team. We already had two defensive beasts in Bradley and Crowder who both happened to also be quality offensive players who could stretch the floor - so swapping either out for Smart would have made us little (if any) better on defence, while sacrificing a lot of offence. That was a big deal, as we didn't really have a lot of offence beyond IT and we really needed that extra scoring from Braley and Crowder.
However now we have Kyrie and Hayward, and those two guys on their own are strong enough offensively to carry the team on that end of the court, while also both being elite outside shooters. Add in Horford and Morris and you have two more guy who can give you ~14 PPG apiece while also helping to stretch the floor with their solid jumpers.
So with four guys out there who can all shoot and score, now we don't really NEED more offence. However I am a bit concerned about our perimeter defence with Kyrie and Hayward. Kyrie is a major defensive liability, and while Hayward can kind of hold his own on that end, he's far from a defensive stopper. I think we really need a guy in that starting 5 who can be a difference maker on defence, and Smart is that guy. With all that scoring in our starting 5 his standard 9-10 PPG would be all we'd need from him, and his inconsistent outside shot wouldn't really be a huge issue.
On the other hand, Jaylen hasn't really proven he can excel consistently on either end of the court yet, and I'd really like for him to have to prove he can stand out and earn that starting spot, rather than just being gifted it. I'm not yet convinced that a Kyrie / Jaylen / Gordon trio can be capable enough defensively just yet. Jaylen was solid defensively at times last season, but he didn't show consistent defensive prowess.