I have a back condition and own a Standardbred mare and an Arab x American Saddlebred (50/50) gelding and my mare is a lot easier on my back than my gelding. I love him to bits but he has a big movement, is prone to moments of teleportation and doesn't believe in walking when he can jog but as long as I remember to take painkillers before I get on him he will go for days and he does have a very comfortable passage...not that we do dressage at a level that requires it ?...my core strength has improved through riding him which in turn has helped my back though.
Just to add my two pennies, we Arab owners do love to talk about how wonderful they are!
Firstly, i had an Anglo, most awful horse i have ever known and i don't say that lightly. He was aggressive and aimed to hurt, he kicked me in the jaw once as he did a fly by, the second time he did it he only missed as i jumped over the fence! But i understand he was the exception as many others tell of how wonderful theirs are.
I then, against my instinct, bought a full, 5 yr old Arab. He is the most wonderful boy. He is friendly, loving and loyal. He is very sharp but also sensible-ish. He has an amazing work ethic and has loved improving and getting stronger. I find him comfortable now he is stronger and working over his back but can be difficult when in full Arab mode and he sinks his back with his head and tail at the vertical!
I've got 2 purebreds I find them incredibly comfortable to ride personally I don't think you can beat them as a riding horse but I have always loved them and ridden many over the years.
They can be hot sharp and they do spook some are worse than others I find you have to give them a job, they are very intelligent and learn very quickly the more difficult things you do with them the easier they are they definitely need to be busy.
They can be the most loving horses and most really love people but they can be sensitive and they don't appreciate rough handling, I do think some people are just not suited to them and then they can end up a bit neurotic have seen a few a bit messed up just from being with the wrong owners.
I absolutely love mine I can't imagine not having them in my life.
My best ever horse was a part bred,she was bred from Cranleigh Red Shadow,she would go anywhere and do anything,if I could have cloned her I would have,my next was a pure bred crabbett tough as old boots
My father had an Arab in Palestine, he bought him from the chief of police and i have the pedigree certified by Arab cheiftains. He was called Prince and it would appear, from the photo albums I have, that he would do any thing: ride, drive, polo, race, be friendly to girl friends, any thing! When he left Palestine he gifted the horse to his groom in the hope that the horse would be happy. Prince was a grey and ever afterwards, at the races, my father would only bet on the grey.