The 3x9 and the 10x HD models have better glass. I think they might even go through different factories. The 5x20 model uses the same HD glass as the more expensive fixed 10x.
From all the accounts I've read at Sniper's Hide, the 10X HD model's glass is on par with scopes in the $1300 range. The 3x9 isn't too far behind it.
IMO, the better glass is nice. But if you're on a budget, I don't think the lower cost models are going to be bad. They're all durable, and all have good glass. The more expensive ones apparently have excellent glass.
