Which style carpet and how does it compare between suppliers?

I saw the following types available from Auto Custom Carpets

• 800 Series Cut Pile
• 600 Series Nylon Loop
• 500 Series 80/20 Loop

And an option for Massbacking.

1. Which type do I want, and why?
2. Is the Massbacking something we want?
3. How does this compare with whats available through Legendary?