Fire Emblem Awakening [SPOILERS INSIDE]

Question: how much does the difficulty ramp up in the later chapters on hard and how bad are the ambush spawns? I currently can't decide wether I'm going to do my first playthrough (once I finally get the game on the 19th) on Normal or on Hard. I'll play on Casual regardless of difficulty so I won't end up ragequitting the game on a bad day.