Tactics. No questions asked. Why? I’ll give you two examples.
1) Our group has a ‘rules lawyer’. When someone wants to know the correct answer we ask him. But, he is not a good player. He has never beaten me. My record against him is maybe 19 - 0. He knows the rules better than me, but can’t beat me. He is not a good tactician and makes setup errors, basic tactical mistakes (stacking) and can be baited into counter-attacking a lone tank while he is on defense which then opens up holes in his defense, etc. Although, he is a superior strategist and excels in wargames like World in Flames, Paths of Glory and Empires in Arms.
I’ll take a better tactician every time, because he will get better the more he plays and learns the rules. Someone without inherent basic tactical skills will not get much better no matter how much he knows the rules.
2) Just played a newbie this Friday. It was only his second game of ASL. His first game on defense. I knew from the moment we started playing that he is going to be a great player. He had an extremely well thought out defense, he asked excellent questions about tactics, he made good defensive decisions and I found myself wondering on turn 3, “Am I going to get beat by a newbie?!!!” Fortunately (unfortunately), he made two critical mistakes that I was able to exploit which turned the game around.
He had almost no rules knowledge, but almost beat me due to his excellent play. Only two tactical errors cost him the game. You can teach rules and you can teach basic tactics, but you can’t teach that particular tactical skill that separates the excellent player from the good player.