Dragon Scale is considered sub-par because it doesn't have any normal defense (even in T3, a lot of attacks do normal damage), and because you rarely need elemental and piercing at the same time.
Using it for Shadow Lair is a bad idea too. In Rabid Snarby Lair, the most common and deadly enemies are undeads, which do normal/shadow/poison : Dragon Scale protects for none of that. For Ice Queen, it's normal/piercing/freeze : there are shield which do both normal and piercing, making Dragon Scale a sub-par choice too.
But Dragon Scale looks ultra cool, at least.
I have both shields, and I constantly use Grey Owlite for FSC. I think, due to having no normal resist, the Dragon would be better suited for Beast strata, or such. I personally use the Dragon Scale for Shadow Lairs such as Rabid Snarby and Ice Queen, but for FSC... not really.
Edit: I should say that my Dragon Set is UV'd, which gives it extra bonus defenses against Shadow/Freeze, etc.