Gaming Minecraft Difficulty difference and mob spawner height?

[Delta517]

So I made a mob killer right at a mob spawner I found. It's working great right now, but I was wondering about the spawn rate and drop rate differences between the difficulty? I heard a lot of things about it, but no one seems sure.

2nd question: I'm about to make a mob spawn tower, but not sure about the height between the floors. So far I have 16x16, but what should the height be?

 

[Kwartel]

Peaceful
Player regains health over time. No hostile mobs spawn. This is with the exception of the smallest size Slime which will attack but cannot deal damage. All hostile mobs will disappear when switching to this mode and neutral mobs will return to their harmless state upon provoked.

Easy
Hostile mobs spawn. Enemies have less health and deal less damage than on normal difficulty. Creepers will cancel their explosions after moving only a short distance away.

Normal
Hostile mobs spawn. Enemies deal standard damage and have standard health.

Hard
Hostile mobs spawn. Enemies deal much greater damage than in Normal Mode, and Creepers will not cancel their attack unless a big distance is between them and the player, making the explosion much harder to avoid.

Dunno about the tower.. (google )

http://www.minecraftwiki.net/wiki/Difficulty