Seriously? My knees are already bashed into the seat in front of me. No way am I letting someone straddle me to get out. I’ll just get up, thank you very much.
It’s the Golden Rule. 
Precisely this. Not only do I get up when someone needs to get past me on the plane, I will insist that you get up if I need to get past you. I refuse to pull a muscle or contort myself to get over and around you. Get up and let me out so I don’t hurt you and me both.
Crotches. They’re what I’m used to.
(nm-double post)
There is an issue here that has not yet been raised:
What gender are you, and what gender and age is the person whose crotch/ass will be in your face?
These are deep, important questions…vital to our understanding of the human condition and the meaning of life. Remember, if the plane crashes, this ass or crotch will be the last one you have ever seen.
I prefer a fat guy to keep his ass towards me, but as far away as possible. But for an attractive young woman in tight spandex,…well, it’s all good. 
Me, whenever I fly it’s usually a 13 hour flight,and I manage to get to the bathroom just fine, without bothering my neighbors. I don’t walk out to the aisle…I vault over the neighbor.
Brace one hand on the back of the neighbor’s seat (on the headrest) ,and the other hand on the seat in front of him. Then in one motion, I lock my elbows so my arms are straight, hop up, bend my knees, and swing my feet over my neighbor’s knees, and land standing up in the aisle. (Try it–it’s easier than it sounds----I ain’t no athelete. But I am kinda skinny. And I never wear shoes once the plane is airborn.)
For me, there’s an element of “go while you have the chance”. There’s going to be a time towards the end of the flight when you are confined to your seat with your seat belt fastened and that time can get even longer if you are circling around waiting to land or stuck on the ground waiting for a gate. I prefer to have an empty bladder when we go into landing mode.
Actually, the reason I always try to choose an aisle seat is so I can get up as much as I want without bothering anyone. And I always get up whenever the person next to me needs to get out. And I’ve also noticed a tendency that if one person in row decides to take a bathroom break, everyone else will figure that since we’re all getting up to let them out it might be a good time to take one themselves.