I haven't been able to locate any numbers to indicate which option I should go with.
Heroic (No socket, not warforged) Tier-17 4 Piece
or
Heroic (No socket, not warforged) Tier 17 2 Piece + Heroic (No socket, not warforged) Tier 18 2 Piece
Additionally, I have a 20% upgrade in the chest slot that I would take advantage of due to the result of this change that isn't a Tier piece.