Having Orks on the brain at the moment I'm liking the look of the Outrider one - a Deff Dread supported by two mobs of Kans. Get a KFF (in a Wagon) behind them and get the Waaagh rolling!Or a trio of outflanking deth-rolla wagons with the Mech Assault.Ambush could be pretty nasty with a KFF, giving the Spearhead stealth and thus a +1 to the KFF's save.Or the ability to field a Reaver in a 1500pt game - Mwahahaha!
Thinking of using the armored spearhead one with my guard. Fill the 3 HS with regular Russes then spearhead a lone Executioner, with Pask. Four Russes, none in a squadron, and the important one has a 5+ invulnerable.
I'm not sure witch one to pick, they seem to open up so many options!