Criollos are well known for their hardiness and calm temperament. They can turn their hoof to just about anything and are very good doers. I think they're rather pricey in the UK, aren't they?
I used to have a criollo ex-polo pony- she was a definite fatty but bombproof as they come and she had the smoothest canter of any horse I've ever ridden. They aren't all like that of course, but by and large, they are nice natured sensible horses. I'd look out for an ex-polo pony as they tend to be cheaper than a specially imported or bred one and have seen it all.
My polo pony was TB x Criollo, and the criollo made her the most pleasant horse to handle - my 2 year old nephew ran in and hugged her leg. I love Criollos, but now have a Welsh Cob! The Argentine ponies are fantastic as they are so laid back.
Banana is ex-polo, believed to have Criollo breeding (possibly x TB). He's a superstar, 29yo, had MOT last week - blood tests came back showing hes fitter than any healthy younger horse, no liver damage/cushings/anemia/nothing at all wrong with him, even his worm count was zero!
He's fun to ride, but safe, tho it took a year to teach him to trot lol, he's spent his whole life walking & cantering. He turns on a sixpence tho so when scary rabbits jump out of hedges, you find yourself heading back in the opposite direction before you even know anything about it so if you don't have a good seat, you might go out the side door :-D
Sixty something friend has bought a Criollo to hack and she loves her! Purebreds seem to fit western/treeless type saddles best - friend bought a synthetic one so not too heavy for her to lift.
They're best if they live out - they get fat on thin air.
Anything that has had polo or western training will be able to turn and move like lightning if the mood takes them, but it usually lasts about two strides
and they are so comfy you'll hardly notice, particularly on a western saddle!
She has them for sale too, but are expensive. Nice horses and well mannered/trained. But I didn't find them challenging enough! Great for nervous/novices though
I rode Paso Finos in Peru when I did the BHS Inca Trail Challenge one year. They were lovely horses. I think they are gaited, they have the smoothest trot. They should make good riding horses.