I tend to agree that stopping on the centerline could be the safest option UNLESS it is immediately obvious where the fire is in relation to the wind direction, and the wind itself is fairly strong. Screwing it up and turning the wrong way could be disastrous, whereas stopping straight will at least ensure that the fire is being blown back (assuming there was some headwind component in the first place). Also there is the issue of easy access for emergency vehicles. In the latter regard, I would never go off the runway onto a narrower taxiway just to face more into wind. Stop, shut down and if fire warning still present, order the evacuation. Leave choice of exits to cabin crew. Without the full picture, very dangerous for flight deck to be nominating exits when they can't see outside. Just because an engine fire has occurred on one side does not necessarily block any or all exits on that side.