I'm hoping some of the guys here can confirm (or deny) a bit of advice I ran across. If it is necessary, after an accident, to remove a child in a 5 point harness car seat from the car; Is it safer to remove the entirely car seat, with the child still strapped in? The logic is the car seat acts like a back board, and minimizes any movement of the spine. or, is there no appreciable difference?

Depends....I was always taught if you can SAFELY remove the seat with the child in it (immobilized-padded etc)...go ahead. If the child needs intervention (ie. airway control etc) then remove them. It all depends-is it intact? Compromised? There is no 'rule'. I was taught to use it as a tool if it helped. If not.....get rid of it.

Personally, I have left many a child in it to get them out. Made things easier and smoother. I know of others that can't wait to get them out of it.

Depends on lots of things. If there is no immediate danger, let the rescue people decide/do it.

If there is immediate danger (fire, drove in to a river/lake), what ever is quickest.

Assume an immediate need to evacuate the car, and that the kid is unable to climb out of an unbuckled car seat on their own accord. I know not to move an injured person unless I absoloutly have to (fire, flood, etc.).

For smaller children, It is easier and quicker to remove the whole car seat from the vehicle than to take the kid from the seat in an emergency. In most cases, we leave the child in their car seat to transport them to the hospital unless the car seat is interfering with treatment.

I would not expect too much difference if you can properly handle both.
If you remove the seat together with the child, you have a place where you can leave the child (of course while keeping a close watch). I would recommend to perform a basic check on the child in any case.