I look at Tatum's skills and body and athleticism and he looks like an NBA star. But, this scares me:

That's a rough shot chart.
Two things:
1) I think the discrepancy here can largely be attributed to the types of shots being taken. Tatum seems to have taken many more of his shots out of isolation; whereas, it seems almost all of Jackson's offense was in the fast break, penetration to the bucket, or on spot-up threes. We need Tatum's isolation/scoring abilities that we currently lack outside of IT much more than Jackson's raw athleticism.
2) Look at their respective strokes. Tatum has a much, much smoother shot than Jackson, who has a major Marcus Smart-esque dip in his shot. Tatum certainly projects to be a much more consistent shooter at this level than Jackson, because that much movement on a shot seems doomed for failure.
Jackson probably has the higher ceiling due to his elite athleticism, but so have many prospects that never developed much more than that, ala Derrick Williams. I think Tatum probably has the highest floor of any prospect this year, and his upside is a more two-way oriented Paul Pierce/Anthony mix.
Jackson is Iggy 2.0 in my mind, which is still good, though not great at 3.