Let me write as a Tech Manager who personally stopped and evacuation:
An EAL DC8-51 had a RMLG downlock failure coming into KJFK. I went out to a runway with the NY Port Authority Fire Chief and viewed a flypast with binoculars and saw the right gear swinging free. So a landing was planned. Crash trucks all lined up and I with the Fire Chief at approach end of the runway. It was then I realized, to avoid blocking the active, they were landing on a runway with a stiff crosswind that was blowing the aircraft toward the bad gear. I protested to the Chief but things were all gelled.
The aircraft went by us and we turned and followed it at full bore. A/C touched smoothly, rolled for a bit and then the RMLG walked in under the fuselage and down she went on Nbr. 3 and 4 engines still going at a fair rate of speed.
Sparks, smoke bits but the plane stayed straight and as it came to a stop Nbr 4 engine decided to catch fire. By then the PONYA fire people had caught up and the engine disappeared under a mountain of foam. I mean that literally.
I jumped out of the car and saw the chutes properly coming out on the port (windward) side and none on the fire side. However, the stiff wind blew them under the fuselage before they really inflated so essentially, there was no usable chute as they were curled under the fuselage. I happened to be Chief of my local volunteer fire department so had some understanding of when a fire is out. I looked up and saw (a DC-8 was a tall aircraft) that it was impossible to use them chutes but I could see the pax upstairs were ready to go. A Flight Attendant was in the door looking horrified. I waved my arms, screamed at them - "Stay - Stay - there is no fire". - I was at the aft slide, I ran forward and stopped the forward evacuation too, they had the same problem. Some people were on the wing and I yelled for them to stay there, no danger.
Later, the Fire Chief asked me if I had the authority to stop an evacuation. I told him I was the Senior Ground Person (a General Foreman) from Eastern Air Lines on the ground and that he would have had dead bodies or extreme trauma victims now if I hadn't stopped them.
Each situation is unique. You have to use some judgment. However if there had been an active fire (say a puncture in the wing feeding fuel) I would have grabbed the bottom of the chutes and pulled them out to the port side so they could have been used.
Staying in a plane with an exterior fire is daft unless the exterior fire surrounds the aircraft. Then you can only pray the fire service can make a path.
And I say God Bless the Fire Services.