These are the stats of the items, which I've put in my opinion of optimal form. The Furious hilt/haft is debatable, but the only real one that will benefit an IMonk, which uses Bonetti's Defense. And the Enchantment pommel/grip is a no-brainer.
Furious Long Sword of Enchanting
Energy +5
Slashing Dmg: 14-21 (Requires 9 Swordsmanship)
Double Adrenaline on hit (Chance: 10%)
Enchantments last 20% longer
Value: 107 gold
VS.
Furious Flame Spitter of Enchanting
Slashing Dmg: 6-16 (Requires 3 Axe Mastery)
Halves skill recharge of spells (Chance: 10%)
Armor -10 (while attacking)
Double Adrenaline on hit (Chance: 10%)
Enchantments last 20% longer
Value: 15 gold
Now, one is a collector wep and another is a crafter wep. Though, the HoD sword can no longer be crafted and is highly sought after. Also, the 15% FFS was not used because:
a) really hard to find, most people who have it won't give theirs up
b) high cost, which of course is due to low supply and high demand
Now, onto the Pros N' Cons!
HoD Sword
Pros:
Unconditional +5 Energy
Moddable, unlike wands, and can add prefixes/suffixes
Can hold gold value (ectos keep getting lower and R/S are unstable)
Status symbol for IMonks
Neutral:
Long Sword, but has a Short Sword/Gladius skin, like the craftable 15^50 Long Sword in Droknar's Forge
Cons:
Quite expensive
The Explanation
HoD Swords are quite hard to find and uncraftable now, so they are quite pricey, ranging from 300-500k depending on the seller and if it has a prefix or suffix. It is moddable, unlike wands, and you can of course add a 20% Enchantment mod or 10% Furious mod. It is like a status symbol for monks to show that they have it. The skin is not extraordinary or unique, but you can prove it in the trade window I suppose. Also, they can be used to hold value, which mine do. I usually reserve their value for gold since my storage can't hold more than 1 Mil and ectos aren't reliable. Ectos drop because of speculation of new l33t armor or something. Rubies and Sapphs are also unreliable as they were 1.5k a few months ago and may go down because of Jade N' Amber. They hold value well and can only go up now because they can't be found/made anymore. Though, this may not be the case in the near future as someone "CLAIMS" to have found an Enrg +5 Oni Blade, unconditional, not like a mod on it, but like an inherent mod. No SS though, so no truth to it as of yet, and if I got an item like that, SS!
Flame Spitter
Pros:
Halves skill recharge of spells (Chance: 10%)
Cheap as hell, since it's from a collector and can still be found
Neutral:
Cool name, but just the skin of a War Axe
Cons:
Too cheap, I might not even mod it.
The Explanation
FFS is really a great IMonk item. Though not of the fame as the HoD sword is, it is really quite good value at only 3 Scorched Lodestones. I know many people who can afford HoD sword, but like the occasional half skill recharge, which can be VERY helpful! The skin is really not an issue, yet it does have a cool name. But it is so cheap, I don't know if I would really consider adding 10% Furious or 20% Enchantment mod. The mods would be worth like 1000x the value of the item itself. Plus it would be hard to sell since other people can just get it and mod it themselves.
The Verdict
Really, it is a matter of preference. Do you like that extra spell, or that spell to recharge faster? Do you like to brag to your friends about your uBeR l33t item, or do you like using cheap, but effective collector's items? I don't know. But in anycase, for the general public, the best value is the FFS. Though you might feel odd about adding mods worth like 1000x the value of the item and it will be hard to sell, if you are really playing the game for performance, you should. The HoD sword just costs too much, much more than the mean of the average GW income (like we have one

Whatever you choose, hopefully you have learned something or been able to connect to something I wrote. HF & GL playing GW!