Each defense is different and does have it’s strengths and weaknesses. You must locate each defense in such way that they complement each other. For example; the mortar does have a slow fire rate but does massive splash damage. making it very effective against barbarians, archers and other tier 1 troops. It’s downside is that it cannot attack troops closer than 4 tiles. Cannons and archer towers do attack single troops, making them more effective against high health troops like the PEKKA or giant. Make sure to spread your air defenses and wizard towers they both target air troops, the wizard tower also attacks ground troops making it a great overall defense.