Now, when you're climbing aboard a Cessna, do you put your left foot on the step first or the right?
But it
does matter if it's a Super Cub you're getting into that you've just shoved off from the dock - get it wrong and you could waste sufficient seconds sorting yourself out that you risk hitting something.
The beginning of my first lesson consisted of getting into and out of the aircraft in a hurry until it was automatic which foot went first and where.