Well, thanks for your reply first.
My question was more in between the 2 scenarios you mentioned. Like you are cruising on a relatively short sector say at 24000ft and then you get an non extinguishable fire. You plan to land on the airport that you just flew over 2 minutes ago for numerous reasons, say its the most nearest in time that will guarantee you an expedited arrival there. You have fired your bottles, you have delared Mayday, and the fire is still there.
Turning back to the airport for vectors and high speed you will have 35-45 track miles. Speedbrakes, preparing the FMS and off you go. Its gonna be maximum 8 minutes till you hit the ILS.
On the one hand you have little time to go through full briefing and on the other hand you have some time left to prepare.
IMHO these are scenarios where in real life you would tell the cabin chief that we are on fire, going to divert there NOW, and you just fly it, have the other colleague check if its something strange in the box and off you go. Whereas, in the sim its a pain in the @ss.