Lately it seems that you should add whatever collectively gets you the highest dps. Other than Blitzkrieg, it seems like everyone is just using nearly all decoys (Myself included) so whatever troop is in there doesn't affect the outcome as much unless the decoys get taken down quickly or an accidental mis click of the decoys which does happen. I like the armored cars in theory as they have a better rate of fire, dmg, and hp. They don't have the splash like howis but the decoys are spaced out so splash doesn't affect them. That being said, it is a burden on oil and they can be taken down like anything else. For general purposes, you should always have howis at the very minimum and use brit shooters to fill in those smaller spaces if any. If you have the oil to use than try armored cars. I've tried both combos many, many times but it hasn't seemed to really change the outcome of a war. From watching, the worse the attacker, the more effective howis are because those are generally the players that will click rally on the town center and get blasted away. I think the average player would expect the howitzer but be surprised by the armored car and perhaps make a mistake. Our wars have really been up and down lately with varying degrees of opponents. Currently its gain 854 glory or lose 70 so I don't expect any combo we use in the town center will matter.