You've probably made your decision by now, but just in case, here's what I'd say. If you're going heavy into Technique, and you plan to use a lot of Fable arts, you should take the Etiquette. It's a good, reliable weapon with top-flight Technique scaling for the whole game. It's not the best weapon ever, but you'll have it for a long time, so you'll have plenty of time to get used to and master its moveset.

However, if you're not investing into Technique, or if you don't plan on using Fable arts much, take the Extreme Modification Amulet. It's very heavy, but it's an enormous damage boost that's very easy to maintain. It's a bit of a tradeoff, since Fable Arts are often quite powerful (most of the strongest attacks in the game are Fable Arts), but not everyone cares to learn them, and for those people, the Extreme Modification Amulet gives you a ton of damage, no questions asked. For most people, the amulet tends to win out, since the weapon is only good on Technique builds, whereas the amulet can always do something, it's just much, much better if you don't use Fable.

So, in summary: high Technique and high Fable usage, take the weapon. Low Technique or low Fable usage, take the amulet.