So currently I have the opportunity to ride 2 different horses. Horse one is 14.3 hh and he is very lazy. He is my daughter's lesson pony and while she makes him look good, when I get on I have a hard time getting all the way around the arena in a posting trot. I just can't seem to find or keep a rhythm. It is like he is fast for a few steps, then slow, then fast then breaks into a walk. He requires almost constant leg. He came to the barn last summer what I think of as a broke but ignorant horse. He was safe under saddle but he was unbalanced at a trot and he is still currently working on consistently getting his canter leads. Horse 2 hasn't been ridden a lot lately but is very nicely trained. He isn't hot, but when you ask him to trot he trots and he stays trotting until he is asked to stop (with an occasional reminder to maintain gait). I can post around the arena multiple times without a problem. I even took him over a cross-rail the other night. It was the first time I had done any jumping at all, ever and it was no problem.
So my question is what make the one horse so much easier for me to ride? Is it training? Or is it that the one horse is more forward? Or is it a match of my natural body rhythm with the horse's? I am trying to figure out an answer to this question because my daughter and I are trying to find our own horse.