For everyone's reference:
http://www.minecraftwiki.net/wiki/Difficulty
Hard References wrote:Hostile mobs spawn. Enemies deal greater damage than on normal difficulty. The Food Bar can deplete and will slowly kill the player if it drains completely. Creepers will not cancel their attack unless a large distance is between them and the player, making the explosion much harder to avoid. Zombies break through wooden doors.
Mobs are more likely to spawn with armor in higher difficulties.
Villagers killed by a zombie have a greater chance of becoming zombies in higher difficulties.
Explosion damage to entities changes depending on difficulty.
Zombie Pigmen spawn from Nether Portals in the Overworld more often on higher difficulties.
Now, before getting into the realm of considering others, I would LOVE to see hard.
Dying of Hunger, Creepers still blow up if you run away (so no more PUNCH THEM ONCE AND RUN BACK TILL EXPLOSION STOPS method of killing creepers, you legit need a weapon strong enough to 2/3 hit kill a creeper), Zombies will devastate villages unless you work hard to protect them, Mods will spawn (and drop) armor more often, ZOMBIE VILLAGERS FUCKING AWESOME, PIGMEN IN THE OVERWORLD IRRITATING MIST AS SHE BUILDS PORTAL IN HER LIVING ROOM FUCKING BAWLIN. Shit's actually HARD, makes you SCARED of mobs again.
Now, keeping in mind that this server IS a COOPERATIVE BUILD server, and NOT a Player Versus Environment server, a lot of that difficulty just irritates players trying to build epic things. So I would suggest normal. You can't starve to death, creepers will stop TSSSign if you run, Is the difficulty that the rest are based off of (easy deals LESS damage than standard, normal everythinng IS standard, hard id MORE than standard, etc), and all around keeps a challenge, while also keeping the server somewhat safe.
Yes, cave spiders actually have a reason to be more scary than regular spiders, because they are rarer, and only spawn in caves. Yes Withers are supposed to exert the Wither Effect. Yes you are supposed to get down to 1/2 heart of health if you don't eat. This is all GUD \o/