In terms of stats, Manziel had better numbers.
But in terms of actual ability as a passer & diagnosing Defenses, they're not in the same stratosphere. Sanders clears him on every tangible & intangible necessary to be a good QB.
Manziel had a ton of off the field issues in college & leading up to the draft, that only became compounded once he got drafted to worse franchise in sports. He was a known hard-core drug abuser; not just a little Coke, but was an opiate pill addict & hard drinker. On top of, having a really really bad work ethic.
I'm good friends with Coach Byron Thomas who was a GA at TAMU when Manziel was there & he's personally told me stories about how Manziel never studied film. And on the rare occasions when he would show up to team meetings, he always late, followed by usually falling asleep halfway through.
All of this was known by NFL front office personnel people before the draft & he still got picked in the 1st round.
It's why what round you get picked really doesn't matter in the grand scheme of things. It's way more crucial where you go, as opposed to when.
The same NFL that drafted Zach Wilson, Mitchell Trubisky, Mac Jones & Mark Sanchez in the 1st round, is also the same NFL that didn't think Brock Purdy was a 1st rounder.
The league is filled with people who don't really know wtf they're doing when it comes to QB's.