I'm taking a look at the shot charts for each
Fox
https://www.statmuse.com/nba/ask?q=de'aaron+fox+shot+chart
Morant
https://www.statmuse.com/nba/ask/shot-chart-ja-morant
Does anything stand out to you?
Fox looks like he is better
1. At the rim (also shot 6.7 FT's a game vs Morant's 4.6)
2. Above NBA average mid range game overall
3. Career .328 career average from 3 on 2.8 a game (I think they both have a lot to prove)
Morant
1. Better near the FT line area, probably with floaters too
2. Low volume mid range game (Means you can roll with his defender more, even if it's not hip for stat guys)
3. Career (well rookie) .335 from 3 on 2.7 attempts a game (I think they both have a lot to prove)
Beyond this Fox is probably the superior athlete, higher potential defender. Fox has a smaller TO per game. Nothing jumps out with assist numbers. You could say Morant is younger of course.