No, it's the captain's call, but 20/20 hindsight makes this very difficult: If he had issued the call immediately, they probably would have opened the doors on both sides, and casualties might have been much higher if evacuating passengers had been caught in the fires on right side, and it would have been easier for the flames to enter the passenger cabin. On the other hand, if fires had started on both sides, everyone might have been screwed. As it was, I believe rescue personnel were working desperately to get people out before the fires reached them. I'll leave it to the pros (NTSB) to second guess this one. I'm sure that's one of the points they'll be addressing. One thing (moot in this case since both engines had separated) the pilots must do before ordering a general evacuation is ensure that the engines are shut down, so nobody is sucked into the turbines or hit with the exhaust. There was an engine fire on an AA jet not too longer ago where the captain deliberately turned down crew members requests to evacuate because he felt it would be more dangerous if passenger got in the way of firefighters.