I'd take Tatum but I think it's close.
I don't think it is. Mitchell is essentially a Wade clone, right down to the streaky shooting. Those guys actually have to be offensive centerpieces because they're not really capable of being secondary scorers. And in the world of primary scorers, Russ Westbrook he ain't.
So if the choice is between a crack whore's Westbrook or a poor man's Durantula, I'm taking the latter twelve times out of ten. Especially given that Tatum rates out as the much better defensive player.
The size difference between the two is a real shortcoming for Mitchell. Despite the arm length, at barely 6'3" 210, unless he's willing to kill himself a la Marcus Smart, there's only so much Mitchell can do defensively against guys standing over 6'6" (and it's a lot easier to go full frontal Marcus when the team doesn't
need you offensively).
Now, Mitchell had a better offensive regular season, but his efficiency nosedived in the playoffs (as it does for those sorts of guys). Tatum's did not, even as his offensive role in Boston grew with the postseason.
Would you take Simmons or Mitchell?
This one is tougher, but probably Simmons due to the size/upside factor. Simmons has the size/athleticism combination that
should allow him to be ideal for the switch all the time defense. And his ability to run an offense is a big plus if he can at least get his game out to the 18'-20' range.
I think part of the problem is that even after firing Hinkie the Sixers stayed on process, and kept all their young guys playing in an inexperienced clubhouse. So there's a headcase factor there.
Mitchell had the advantage of stepping on to a veteran team that could help him maximize his potential. I've been saying this for fifteen years now, back to the days when I said that the best thing the Cavs ever did for LeBron was clearing the talented headcases out and giving him a veteran clubhouse. I think this was a huge factor in Jaylen Brown's development, as well. There were guys here to teach him what it took to succeed at this level and he had to earn every minute of playing time.
So this one is closer, but Simmons has a lot more upside, and I would probably gamble on it.