Thanks for the input folks!
This barn will be primarily for personal use, with the exception being friends or a couple of weekly students coming to ride. The only needs I have to accommodate are my own. 
I am leaning towards the double sliders, and as someone already mentioned, an open porch or overhang would probably reduce the impact that snow/rain/etc has on the doors.
Whatever kind you get, try to incorporate some windows for light in the barn.
That can make a huge difference in how much light you have in there.
Two sliding doors on each end. Easy to open with one hand, for the past 9 years. I have been told that if they get out of adjustment, that it is simple to fix that. So far though, no issues! Love them. They look great open or closed and do the job! We got ours from Lucas Equine Equipment. And the aisle is fourteen feet wide, plenty of room to drive down the aisle. The only problem with that is … my husband has decided to park his new tractor in there, so you may NOT want a nice wide aisle
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I boarded at barns that had both. My personal preference is the double sliding door. You can easily open the door one handed and walk your horse in. Something one barn had that was pretty awesome was a walk door on spring hinges in one door. You could open the door and step in instead of sliding the whole door.
Sliders or overheads (garage doors) both do the job, both have some pros and cons. I have had both. Personally I prefer sliders.
Sliders when installed properly on quality hardware as Clanter pointed out open and close easily.
They are easy to build, and install in my personal hands on experience.
They are much cheaper to install verses a quality made and stalled overhead garage doors.
IMO they are much more aesthetically pleasing.
Depending on the size of the slider it maybe worth installing a door. Very easy to do and provides quick access in and out. Esp in bad weather.
Cons;
If the doors are facing into the prevailing winds they can be hard to open because they are pressed into the barn walls. This can be addressed by adding " guide wheels" in the appropriate places.
If located in snow country, snow can and does blow under them. The amount of which depends on the installation. A “fold down” gasket can be fabricated and mounted on the bottom.
If installed in “guide channels” in snow country, sub freezing areas the bottoms can freeze fast. If one remembers to salt before the weather sets in not a big deal. I have always been able to free the frozen bottoms by kicking, rocking the doors. It’s never been much of a problem with our snowy, cold winters.
Garage doors
Well made properly installed garage doors are easy to open as long as they are kept properly adjusted when needed. Cheap ones are noisy and can fall out of adjustment pretty easily.
As others have said most horses get used to the noise.
If the barn is on the narrow side an “extension rail” maybe needed for Sliders. So overhead maybe a better choice.
Cons
The bottom can and do freeze solid to the ground. IME much more difficult to free than sliders.
If the barn has a low ceiling garage doors will lower it even more.
If the barn has a high open. “vaulted” ceiling garage doors will stick out like a sore thumb. This an aesthetic call. Though it can be problematic with horses that may rear.
Overhead IME are much more expensive to have installed. Esp quality ones.
As to 1 or double sliders. IMO this is an aesthetic call. Both work the same.
If installed in “guide channels” in snow country, sub freezing areas the bottoms can freeze fast.
you can put gutter heat cable in the guide groove… down here in Texas we have have to pull this type of heat cable through v groove track to keep gate rollers from freezing to the tacks
something like this… but there cables that you cut to fit also
http://www.morelectricheating.com/pr…iAAEgIuWPD_BwE
If the barn has a low ceiling garage doors will lower it even more.
overhead doors can be install on track that can follow the pitch of the roof line or low headroom track can be used… either adds to material and installation cost
but as gumtree has noted… slide doors can be field fabricated if desired at a faction of the cost of a commercial overhead door. Nor does not require specialized tools
