Chaos Indomitus pattern. I like all the loyalist patterns and even run Cataphractii for my Iron Warriors because it looks great. Chaos Terminators pull ahead for me though. All loyalist patters are clean, mass produced, and honestly pretty simple looking. Chaos Terminators are individual suits. Not one CSM Terminator (lore wise and model wise if you're not lazy) looks the same as the others. Loyalist Terminator squads are just that,a single unit. CSM Terminators are a group of individuals working together for personal gain. Each suit has been fought for hand and fist with the current wearer more than likely having killed the previous wearer. Loyalists can earn the Crux Terminatus by proving themselves better than their foes. Any Traitor wearing the armor proved himself better than everyone who had it before by currently being on the top of the murder-chain that is Terminator ownership.
Plus the tusks are pretty damn cool.