3D, first lets mention head aches and eye fatigue. you have to set your adjustments to what is correct for your eyes, then you will not get the head aches and eye fatigue. I have watched 3D for hours and hours, no head aches, no eye fatigue. no problems. here is why.
when I watched my first 3D movie, I had eye fatigue fairly quick and a light head ache, I thought crap, 3D and cannot use it. then I decided to freeze the picture in 3D, on a good 3D scene, best ones are with water, glass and small moving objects. so I did the one with water from the movie IRobot, I then did my adjustments, found that brightness of medium my eyes liked the best, on 3D depth, when I went more positive the picture was too close to me, more up on me. when I went more negative, the picture looks further back into the wall. negative four looked the best for me at the distance I am from the screen, so that is what I went with. now I have been able to watch 3D movies with no eye fatigue, no head aches, one day, watched four of them, one right after the other, no problem.
next 2D or 3D, anyone that says they prefer 2D, they have not compared a 2D and 3D with a properly set up for them projector. I had a friend come over that said 2D and how Great the picture was and how 3D was not needed, then he watched Top Gun in 2D and then we watched it in 3D. within five minutes of the 3D movie, he said ok, your correct, 3D is better. in 2D, the things in the back ground, your mind does not pick up on them as quickly and easily as it does in 3D. in 3D the items further back are still a part of the picture, in 2D, those items are meaningless, your mind skips right over them.
sure they might not be of any importance, but they are there and when added to the picture, it makes for a better viewing experience.
so 3D is not all about things jumping out of the screen, its about being able to see more items and a more real viewing experience.
a bullet going thru the air looks a lot different in 3D, then in 2D, in 3D, being under water looks like your under water, in 2D, sure, I know the idea, but it does not look anywhere remotely close to the realism of 3D.