The Criollo get's awesome with age ... tons of buttery flavors. The America improves with age as well. I like the Italia personally, reminds me of an Oliva G Maduro with more character.
The Brazilia gets my vote out of the 4 as well ... though the aged Criollos really are great.
The Vision, La Traviata, MX2, LX2, Black, the aged Golds from 2002, Brazilia and aged Criollos are all definitely worth trying (in order of my favorites), imvho.
For those that like that spicy + sweet combo like I do, I really recommend the MX2 (or MX3 if you can find it). They need to be dry-boxed for several days at least, but they are very tasty!