I am running a very terminator heavy Deathwing army right now. I have 25 thunderhammer/stormshield terminators with one cyclone launcher per unit, Belial, a Librarian in Termie armour, 3x3 bikes w. 2 meltas, and 2 attack bikes. It is a very compact army that is hard to dislodge.
I have had a tremendous amount of fun with this army. It isn't over the top, but it is also forgivable. I have had an equal amount of wins, losses, and draws with this army and I am still getting better with it.
This is one of the lowest model count armies out there right now that works well.
I have seen a few different builds for Loganwing, but I am just not that familiar with them. I think they end up being able to do about the same thing as the Deathwing, but they end up costing more.
I can't wait for some cool Grey Knights lists to come out, as much fun as i had putting together my deathwing I can definitely see myself building up a second terminator army.