>>29645900The main game should be harder because there are SO many ways to make it easy (levelling up, getting a specific team to counter your opponent's weakness, etc.)
The post game towers/maisons are usually pretty unfair with the RNG. Since you can only use 3 pokemon and you're facing off a string of 50 trainers it's only a matter of time before the AI throws out a team that can perfectly counter yours, or faint a critical pokemon that you absolutely need to fight one of it's remaining pokemon.
tl;dr main game you have a shitload of handicaps, post game gives the AI everything they need.