There is an age old saying "you can't ride bloodlines". That being said, I have a mare who has fabulous bloodlines, Polish bred, she has done ok in endurance. I have a grade Arab who has done fantastic. (I happen to know he is an Egyptian because I know where he came from, he was just never registered). And I also have a little half arab right now who has been the best horse I have had. He has CMK bloodlines on his dams side and is going to make a great 100 mile horse. But I have seen rescues do great, Spanish mustangs do great, gaited horses do great. We even have a Welsh/POA in our region who does 75's and 100s as well as being a 3 day eventer. I tend to look at the confirmation of the horse. The bone, the shoulders, the hips and judge a horse from that rather than bloodlines. I have seen horses with fabulous bloodlines, like my mare, just hate the sport and not do well in it so take that with a grain of salt.