While some breeds tend to have like characteristics, it is not so much the breed but the individual horse. For example, there are a lot of people saying not to get a Thoroughbred (TB) unless you are extremely experienced due to them being incredibly unpredictable, hot, and flaky. While many TBs may be like that, that is no reason to label them all as such and give people a reason to potentially fear their horse simply for being a TB.
I will not comment on their supposed temperament, but I will say that they tend to be more prone to eye and some skin problems compared to some other breeds.
"I hear and I forget. I see and I remember. I do and I understand." - Confucius