My favourite variant is the Protector.
I play it as a brawler and as such I don't like XL engines on it.
I run with 2ML, 1 LPL, 1 AC20, AMS, ES, STD300, close to max armour and about 4t of AC20 ammo.
With the structure boosts it has, the durability of a STD engine and a pretty accurate and high Alpha, it's a great game changer mid-late in a match. Torso twisting in an Orion is actually fairly quick and allows the damage to be spread well. Usually one side is cored/gone and still leaves a heavy weapon smacking mechs about.
Note that I play normal matches and not CW.
J2L.