Looking over the four non-raid sets, I think it works as follows... Wildheart is good for healing/long duration caster DPS, Feralheart is good for more high caster DPS (less duration, but still) and bursts of feral work, while the epic PVP set is great for feral of all kinds and for high burst damage/PVP style casting... superior PVP set is basicaly a less powerful verson of the epic set (obviously).

Some of you, like me, are looking to invest in the PvP gear for the run speed set bonus for the long run to 70. The epic gear set is a wiser investment, as the gear will last well into the mid-60's, versus the blue gear set, which not only will be worse than the very first expansion gear you will encounter, but it will eat up one more item slot for the set bonus.

If you're Feral and just want 3 pieces for the set bonus, your best bet is to go with the Helm, Chest, and Legs. They are the only pieces of the 6-piece set where the itemization cost has been spent on +melee crit. Note that these are the 3 expensive pieces of the set, and will set you back 39.7K honor. It's worth the investment, as you won't find the run speed bonus till 70, and you'll want the gear to last for awhile. (Good idea to put Clefthide Leg Armor on the legs.)

If you're Resto or Balance and just want the 3 piece set bonus, go with the Gloves, Boots, and Shoulders. They're the 3 cheapest pieces of the set, setting you back only 25.2K honor, and don't waste itemization cost on +melee crit, while still having +dmg/heal.

Lastly, I wouldn't bother buying the entire 6-piece set unless you plan on being a 51-60 AV superstar. You'll be rapidly replacing your gear once you hit the Outlands.

Best for Feral because if you look at the Stats: Agility is way higher than Intellect; movement speed increase in Feral forms; +Agility with all 6 pieces.