I have my DS (1) in a rear facing seat in the middle, my DD (3) behind the driver in a 5 point car seat and my DD (2) behind the passenger in her car seat.
I go in through the rear passenger side door, step up reach over and un-click DD (3) belt and she can climb out as I am taking bub out and into the pram and then undo DD (2)...I feel it is the safest for us.
I think that in the event of a front on accident the back of the rear facing seat would take most of the impact of anything that hits it...protecting bub...if it was one of the girls they would get the full impact of anything coming through.