I just had a barn built 3 years ago. Some of the issue, unfortunately boils down to $$. I ended up with a 7 stall barn, 12 ft aisle, 6 of the stalls are 10x10. The 7th stall is 14x14 across from a 14x14 tack room. The 14 ft stall belongs to my draft. I have sliding doors on the front & back (all the little extras like sliding doors add cost.) plus a "man" door.
The building itself was $23,000 plus chat for leveling the ground (it was fairly level to start with but by laser..still required 10 inches to level.
Then there was the cost of running electricity & water over..each of those $3000 & $1100 respectively so my point is keep an open mind about the larger sizes because you might end up needing to downsize that idea (unless, of course money is no issue for you)
Horsepower: the extraordinary capacity of a horse to elevate the human spirit!
My castle is my barn ;)