I don't care about a pro-style offense. I care about being able to read an NFL defense.
Like you, I prefer Winston as a prospect over Mariota but I don't understand how you can say for certain that Mariota can't read an NFL defense when he hasn't played a single down in the NFL yet. For me, it's more useful to look at whether or not a college quarterback can consistently progress through his reads (which is what impresses me so much about Winston).
The threat of Mariota running against CFB teams is huge - it opens up so many options. The same can be said about Manziel. That isn't going to happen consistently in the NFL.
While this is certainly true, you can't say for a fact that he won't be able to consistently use his legs in the NFL when so many running quarterbacks have been finding success recently (particularly, Russell Wilson).
Manziel was making NFL throws into windows. Mariota doesn't do that too often.
I don't know how you define "making NFL throws into windows" but the truth is that no one is going to know for sure whether or not any of these quarterbacks can throw into tight windows in the NFL until they actually play in the NFL.
If Gus Malzahn/Jim Harbaugh/Mark Helfrich was the HC and he wants Mariota, then fine. Anybody else...nah.
If our new front office/head coach identifies any of the quarterbacks in this draft class as "their guy" they should do whatever it takes to acquire him. I'm not going to go to the extreme of predicting a quarterback that we draft will be a bust simply because of who we decided to hire as head coach.