Because we haven't had nearly enough discussion on this topic, i figured I would weight in on it.
I'm not a Ewers or Card guy either, I'm 100% whoever will run the offense the way Sark wants and needs it to be ran and can win games.
I saw some really good things from Card towards the end of last year, but I do believe he is somewhat limited. I don't think he goes through his progressions quickly and gets happy feet too fast (coachable). He is really good at 1, 2 go. I also don't think, which has been discussed ad nauseum, he can take the top off the defense with downfield throws on a consistent basis. This will limit the playbook and allow a defense to play closer to the LOS. One major plus is I think he is crafty and agile which might come in very handy with a young OL.
Ewers is a gunslinger and can make every throw in the book. Having him back there completely opens up the playbook and could make things easier for Bijan. Not 100% sure about his mobility, but I don't believe he is as mobile as Card, but I also don't think he is a statue. The big negative on him (and it's a huge one) is that he is a gunslinger and will turn the ball over. Those turnovers will cost the Longhorns valuable possessions and could cost them games. Big risk, big reward type of QB.
So, I have no idea what Sark is going to do. Playing Card is going with the somewhat safer pick and will put the offense on Bijan's back (as well as the opposing defense). Going with Ewers makes things wide open for the offense, but is a HUGE gamble that could completely backfire.
If it was me, 20 years ago I would go with the safer pick and go with Card. Today, now that I'm older I'm much more the gambler type and would say F it, lets role. Thank god I'm not the head coach and have to make that choice. I have the luxury of sitting here giving my opinion behind a keyboard with no consequences.