I heard a report somewhere, somewhen,that talked about guide horses...

Some of the resons given for choosing a mini horse as a guide animal were:

That hooves were less tender than paws -- didn't get cut up on pavement and such...

Horses have more stamina to go long distances than dogs (But they wouldn't need to have more stamina than their human guide-ee, anyway)

Horses have a life span closer to humans, so that a blind person could have one partner for life, whereas dogs get too old to do the work around 12 or so...

But of course, this last one only holds true if the human partner knows how to take proper care of them... :-(

All in all, sounds pretty bogus to me...