I LOVE Spanish Arabians! I had a gelding I just sold out of Nina Querida, one of the most accomplished imported Spanish mares to the US.
His bone, hooves, and legs were incredible. Put a lot of the local QH's I rode with to shame. :)
Do you think the Spanish lines were bred more towards being a good bridle horse? (its on my bucket list to vacation in Spain and ride a bridle horse!)
The arabian I had was a grandson of Grojec and he didnt have a particularly dished face at all and like his ancestor was quite stockily built and very versatile - no spindly thing that looked like his legs would break on the first bit of rough ground
You can find old pics of arabians on sites like All Breeds Pedigree and its interesting to see that the further back you go the more functional the horse looks. They had to carry a man across rough inhospitable terrain so needed to have a lot of power and stamina.
Sand is surprisingly really hard on hooves so I would think that the horses with the hardest hooves survived better and were more prized.