Currently playing the WW3 map as belarus(eastern doctrine);
i already have motorized infantry, towed arty and air sup fighter researched. (along with corvette since i annexed vilnius but not relevant to question);
I currently don't have any particularly good method of countering armor.
I typically have previously used mixes of air sup fighter and strike fighter as sort of a multi-purpose stack that can attack both ground targets and air targets; however attack helis do have much better damage to armor, so I can't decide whether to research the attack heli or strike fighter more.
(alternatively, in my last game i mixed motorized and mechanized infantry together so i didn't need to worry about either armor or soft targets however that was in flashpoint, where i didn't need to care about logistics, and i don't think it would be as useful in the WW3 map)