Ignoring stats like %crit and attack power on a weapon and going for pure melee damage, dual weild is probably better, I don't remember the exact mathematics of it but I seem to remember it being true.
However, a hunter is not going to be meleeing for a long period of time. A hunter is going to be running through a mob or person to WC + RS. This means that you want that one hit to do as much as you possibly can. Now you could say that with your off-hand hitting as well, that would still do more.
However, this logic is flawed, because two handed weapons tend to hit much slower, meaning that with a similar dps weapon, that one hit will be much harder.
So to simplify: if you want to extensively melee, play a warrior or rogue, or failing that dual weild on your hunter. If you want to kite and do damage, have the slowest 2h weapon you possibly can.
Now, I have completely neglected stats. Random BoE green 2hs will more than double the stats of a one handed weapon, meaning that for most of a hunter's levelling he should use a 2h. This changes slightly in the endgame where you might have to choose between dual dawn edges (1% crit on each) or a barberous blade (1% crit and 60 attack power or ~4.3dps).
This is more of a personal preference, but here is the mathematics behind stats (crit and dodge scale with level, what is shown here is for a lvl 60 hunter):
1agi = 2 range attack power so 7agi is 1dps
53agi = 1% crit (approximate)
26agi = 1% dodge (approximate)
1stam = 10 health
1int = 15 mana
You can find your crit rate by mousing over the attack icon in the spellbook, however crit rate is also affected by weapon skill so bear this in mind, if you are comparing 2 x 1handed axes to a polearm and you have 300 in polearm and 150 in one handed axes then of course it will look like you have a lower crit rate. Your melee weapon skill doesn't affect your range crit rate, but it does affect melee crit rate (which is shown in the spell book). You need to add 5% to the crit rate if you have the Marksmanship talent.
Heh. Hope I've covered any possible questions.
Edited, Thu Jul 7 00:26:45 2005 by Lobsterok
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60 Night Elf Hunter - Dunemaul (Europe)