Established pitchers are no less likely to get injured than pitching prospects. Obviously I understand the argument - that you are reducing the risk of them busting due to ability by getting them once they're established. But you're also going to pay a serious premium in hitting talent at that point, like the Cubs did. And hitting prospects have their own risk of busting, though it is slightly lower than pitching prospects.
The Cubs paid $2.8 million for Jimenez and eventually flipped him for Quintana. From that standpoint, it's obviously a huge win. But Jimenez's value had dramatically increased since his signing. Could they have spent that $2.8 million on multiple pitchers and ended up with a similar likelihood of eventually ending up with a pitcher like Quintana? I really don't know. They had to pay more for the premium hitter on the international market than they would for a pitcher, then they had to pay more in hitting talent for an established pitcher.
I'm sure this can be determined, and I would like to see it. But every team in baseball, the Braves included, is taking a similarly-talented hitting prospect over the pitcher. That's really not the discussion.