If someone set my horse on fire and the damage was extensive, I would probably put her down as well. Mainly because of the cost it would take to rehab her. I don't have that money.
If someone set my horse on fire and the damage was extensive and I DID have the money, I would have to look at the horse's chance at rehab, how long it would take, how much pain she would be in and for how long, and if she would recover well. I know a lot of burn victims have nerve damage that they have to live with for the rest of their lives.
It looks like NorthStar might have years of recovery on his plate (just read that). Not just months, but years. I think I would have put him down as well. But his owners choose to keep him alive...and if he survives, he can be a pretty good poster child against animal cruelty.
His owners are pulling for him though. I hope that if he DID take a turn for the worse, they would reconsider their options. But for now, he seems to be getting the best care he can. We'll see what happens.