I don't think Noonan will stay at short. His arm just isn't strong enough or accurate enough. I'd expect him to find a home at second. Offensively, he doesn't have a lot of power nor projectable power. Despite being a high school draftee, I'd expect him to move quickly through the Giants system provided he can make the adjustment to second base without a major hitch.
Tejeda of course is the more toolsy player but, like Noonan, lacks power and power potential. His defense is likely more suited for the outfield. He has a pretty good arm and range is very good. He's got a very nice swing but does get a little long. I think he's going to struggle moving up more than Noonan.
Overall, Noonan is less of a risk but his ceiling is far lower. They are close in age and have similar offensive profiles. Neither is likely, in my opinion, to stay at short. I'd take Tejeda for his potential over Noonan but Noonan is the far safer bet.