I don't have any pearly pony so I didn't know that pearly ponies had mostly bad quality hair D:, most of my ponies have a 8/10 quality hair but the problem of the most of them is the tail, especially on the 20cm ponies, their hair quality is nice but when you first take them out of the box their tail is awful, I had to shampoo all of the tails.
I also had a quite strange issue with the talking Princess Cadence, her hair and tail quality was nice except for the color pink, it was super frizzy and awful but the purple and the yellow were perfect.
Edit 31/01: So, today I bought a pearly Fluttershy, luckily her hair is soft and of a nice quality, but my only complain is her tail, her tail is from a nice quality too but it mismatches the hair.