Yes I think about this. It seems to be an issue that causes a great divide in our society. Seriously. People, myself including, are so opinionated they will actually switch the roll to their way while at a guests house.
For the longest time I assumed my opinion (and compulsive need to switch the roll my way) came from a long line of mothers... my mom gave it to me, she probably got it from her mother, etc. Then I started to realize it was more than that for me, so I made a chart:
Ok. So I'm a FIRM believer that the toilet paper should roll under and here's why:
It works better. I've noticed that when the toilet paper is in the over position, it is too close to me to get the optimum pull. I have to adjust my body, use both hands in an awkward way, both of which take away efficiency points. Having the roll go under, on a pretty full roll, could give you up to three more inches of pull room...
Aesthetics... ok I realize that I can't just say it looks better (which I believe to be true) because that can't logically be argued. SO I pinpointed why I like the looks of under better. In the over position, the toilet paper dangles out into space, whereas in the under position, the paper dangles close to the wall (or the pole of a free standing holder). I think this is less of a disturbance to the overall look of the bathroom. The wall is already there... so having the paper hang next to it seems logical. Why create another vertical line into space by having the toilet paper hang out into it, even if it is only a matter of a few inches??
Mechanics The under pull is clockwise and the over pull is counter clockwise. I think I'm generally more comfortable with a clockwise motion... perhaps this is conditioned into us and really shouldn't matter. Regardless, the over pull roll AT you whereas the under pull rolls away from you, which feels less aggressive.
Now, I'm interested in people who think the other way is better and I want to know why.