well to be honest I don't see how it really matters whether or not the photo is 8x12 or 8x10 if you're shooting digital. I've never shot digital so I don't know what you're actual dimenstions are of the pictures.
What I can tell you is that when shooting 35mm film the dimenstions are 4x6 for normal prints at any lab. It works out to exactly 8x12 when you enlarge them. Even though 8x10 are the most common professional photographs, 8x10 is not the actual dimension of a 35mm photograph. To get 8x10 you either have to crop it when developing or develop the full 8x12 and crop it after. As far as the 11x14 goes it's the same ratio as 8x10 so you'd have to do the same thing.
My theroy is that people who now shoot digital are still thinking film.
Alright this got long, but basically. 8x10 is most common, but 8x12 is the true dimensions of the photo (film). Most people enlare 8x12 then crop to 8x10 however they see fit to crop it.
I hope that helps even if though I think i went all over the road.