If you want to frequently board/evacuate the vehicle on the move, then you still need a swing door. Since Russian/Chinese idea for IFVs is to accompany the infantry/tanks and break through enemy line, the swing door would remain their first choice while ramp door is more like an alternative.
American IFVs are more like APCs with better weaponry -- to unload the infantry and provide fire support. Thus it is more comfortable to use a ramp door to un-borad when the vehicle stops.
Indeed ,we haven't had a west vs east peer to peer conflict to test which one of those approaches is more effective .
What role a IFV should perform , or more specifically, just what role the infantry should perform in an assault against a fortified enemy.
I am not sure which one of the ideas is better , a point could be made for both , you can unload your foot mobiles farther from enemy line to provide fire supp or the infantry should be closer and used to clear the tranches.
