Every faction is has their disadvantages and advantages against each other. However, it doesn't mean that any match up is equal at any of the 4 stages: Entrance Play, Early Game, Mid Game, Late Game, End Game.
Based on my experiences, a fair duel should always end mid-game on a 64x64 map and late-game on a 128x128 map. A good map has exposed Natural Expansion, no excessive resources, clear and direct paths to the enemy, and reasonably close gold/stone to HQ.
Lets analyze the 4 stages of the game.
Entrance Play is when players pick their stratagem and follow through. Players on both sides would use their starting forces to scout for "cheese". A cheese is a strategy designed to cripple a player using unorthodox strategies. Rush Builds tend to fall under this category. Next, one of the player would retreat from the engagement and take a more defensive stance. The Defensive Player is B and the Offensive Player A. Player B is currently in a "shell", where he doesn't know what is going on and Player A becomes the "eagle", where he sees all movement. Player A will use this time to expand while Player B will mass units to break the contain.
Early Game is when both armies attempt to stop each other's interests. One player would try to expand and the other would try to stop that from happening. Then, a short series of skirmishes would take place, but no player would sacrifice their entire army in a battle. Players at this stage should pay attention to each other's army composition and devise a plan to counter. For example, if Player A uses Thors against my Spearmen, then I make Catapults to wipe the Thors. However this could backfire if the enemy saw this coming and added Crossbows. Players pick their desired tech path at this stage.
Mid-Game is when both players are combat ready and are preparing for the late-game stage. During this period, armies would clash until one loses their vanguard and retreats. The aggressor would take advantage of this and expand rapidly; thus gaining a huge advantage. Often, players during this stage would suffer severely and lose their natural expansion entirely(expectations are that the player would expand to their natural at least during this stage). In other words, this stage is a tug of war.
Late-Game is when the economy allows both players to throw endless soldiers at each other OR stay in a deadlock with a no mans zone in between. Occasionally, players would twist their army composition or use guerrilla tactics to harass enemy production and resource collection.
End-Game. This is a situation where both player's economy are unable to support its production facilities. Both players resort to early-game army compositions or use unorthodox methods to harass the already exhausted economy.
