Era 1 is raw power, when 2 allomancers fight it is usually one with more raw power that wins
Era 2 is more skillful, there aren't as many of them and their abilities got an upgrade, so they are more tactical about how they fight, The only real allomancer from Era 1 i can see beating Wax or Wayne is Vin or Kelsier - Marsh obv same as Lord Ruller - but those are basically gods.