First, the Vault drives can not be used in a Pool.
Second, Raid 6 (two parity disks) provides the best protection, but also has a performance penalty. For SAS and SSD disks Raid 5 is usually best for both performance and protection. NL-SAS should use Raid 6.
I'd also recommend that you review the latest best practices guides for VNX with MCx available on support.emc.com in the Support By Product/VNX5400/White Papers area.