You have his passing and rushing stats reversed. Source: Rivals.

When I watch him on video, he looks like only 6' tall, not 6'2" as listed. He also doesn't look like he has true 4.4 speed (more like 4.5 or 4.6 but is extremely quick to change direction, strong in the grasp, and usies his blockers amazingly well. He also has solid passing mechanics but lacks confidence in reading coverage (the receiver has to be open by 10 yards). We all know that athletes, especially those 6' or less, inflate their height. Why does this matter? The likelihood that he will succeed at QB is likely directly related to his height. If he's only 6', I think Mack is uncomfortable taking him as a QB.

There is also next year's recruiting to consider:

Gilbert has a shoulder injury that could become chronic
Shepard is a project for an offense that likes a 50:50 pass mix
That means that the success of the Longhorns in 2010 and beyond will depend on who they recruit next spring. If they already have 2 RS freshman QB's at the top of the roster, no top-flight QB will commit in 2009, leaving the cupboard once again bare.

On the other hand, a bird in hand..., avoid overthinking this and offer a QB scholarship, figuring that you'll find a way to turn him into Antwan Randle-El (who was only 5'10").

One other 'con', and biggest one IMO is that if we offer Shepard, Gilbert may not come here.

Also, 40 percent passing rate is NOT acceptable for a quarterback. He hasn't shown that he can even be a dual threat   (passing + rushing) quarterback.

How is he really better than chiles?  Chiles was a 5-star athlete at one point.
I wish these athletes didn't all want to be QB's there's lots of opportunity at other positions.  Look at Percy Harvin, or Joe Mcknight, Jeremey Maclin (sp?).  They can, run, catch, take a direct snap etc.  You dont have to be the quarterback to be the star.  In fact, I'd go as far as to say you have a far smaller chance in the pros as a quarterback, than say a receiver, RB, tightend and so on.  

Vince Young was truly something/someone unique, and may never be duplicated.  Of all the duelthreats I've seen, none appear to be as elite as Vince.  Pat White is short, and can't really throw a whole lot aside from playaction, Tebow is more of a bruiser than finesse, Dixon, well he was to skinny and so on.

VY was an outlier from the mean and people need to see that running fast/elusively doesn't automatically make you a good quarterback.  A playmaker in certain situations? absolutely, but not someone who takes all the snaps.

...but Gilbert is a QB.

....a thought. Perhaps Mack doesn't have a feel for how many QBs he'll have on campus in August. He might have a better feel for the situation after March 29. I can't help but believe he is asking for some time to evaluate. I just don't want to see us slow-play him like we did Chase Daniels.