How big is the QT compared to your display? Also, how did you plan to properly QT the fish with SPS in the tank? The fish may be picking coral due to size of QT and the fact that there are corals right there to tempt it to pick. In a larger reef tank, as many other RC members have shown on these forums; Angels aren't necessarily as destructive as they are portrayed.
My experience with Griffis is that they can get the same bacterial infections as Bandits due to "pinning" the swim bladder. However I found that the Griffis took to eating quicker and to tank life easier than Bandits. I lost mine when it jumped and landed on the top of the tank and got fried by MHs.