Just like every decision to come back or not, risk vs reward.
Physically he hasn't looked fully healthy for much of this year, so maybe he could get stronger & more healthy with another year at UA. He could also just become a more complete player w/ the experience.
On the opposite end, he could obviously re injure himself. He hasn't been dominant but he has some good play on film. Also, I'm not convinced that another year can fine tune "instincts". When you look back at the great UA LB's in recent history, a guy like CJ Mosley stands out just because he had those instincts. Great combination of diagnosis and ability to get to the RIGHT action very quickly. Maybe experience helps that though?
Either way, he's been a warrior. Dude has been battling through a serious injury and helped this D become very formidable. I hope he cashes in at some point!