I full length resize and I crimp, which seems to put me in the minority these days. My ammo generally shoots a bit better than MOA, and while confidence building, this is far more accuracy than I can manage from field positions other than prone. More importantly, my ammo functions every time, even if a round has been left in the bottom of the magazine for several weeks and has had a few dozen rounds fired over it. Every time the rifle fires, the nose of the bullet is driven into the front of the magazine with enough force to push it deep into the case, except for the crimp. What happens then is there is some slight shoulder expansion, but not enough to prevent easy chambering. Had the round been only neck sized, I doubt it would chamber. Should I have to chamber the last round from the magazine, chances are I need it bad.
Beyond the reliability in my own rifle, it seems that from time to time there are some folks who need to bum ammo. If I neck sized my ammo it wouldn't do them much good, then I would have to turn them away or scramble to load them some stuff that will work in their rifle. Often a family hunting trip includes several rifles chambered alike, so there is another good reason to full length resize, and seat the bullets to a standard length. The crimp properly applied to a bullet with a cannular will uniform the pull weight and benefit accuracy.
I'll take a presumptuous leap here, and suggest that, with the exception of .303 Brit shooter, many handloaders who neck size only, also seat their boat-tail spitzers out far enough to either engage the rifling or sit just off the rifling. IMHO, this is going to sooner or later lead to the bullet getting stuck in the throat and dumping the powder into the action. Chances are just as good that this will happen when you are in a hurry.
As stated by other posters however, regardless of the type of sizing used, any ammo going afield should be checked for functioning in the rifle first.
