Hatchback or not - it does not makes a lot of difference. I would go for doors and install speakers there. After all car manufacturer specifically designed so. When choosing the speakers make sure they fit depth-wise, some might have too big magnets on them.

Having speakers in my doors for 16 years now - they work perfectly, no corrosion whatsoever. The only quirk are the wires - you need to make sure they don't obstruct windows going up/down. (I had windows and locks replaced a few times and each time I assembled the door I discovered that wires were in a way of a window, had to redo)

Speakers in the boot are usually complementary to the speakers in the front, they add more power and surround sound effect (when properly balanced).