[quote=KabenSaal]
You can use Observation Haki to increase your attacks. Armorment Haki makes you metal, Observation Haki gives you sight to slip past the enemy guard and break their collarbones.
[/quote]

What? No you can't. Observation Haki just gives you a sixth sense, fighting wise the rest is up to you and what you know.
Not to mention just because someone has Observation Haki and can slightly predict what moves your opponent will do won't mean you can actually get past them, like, good luck trying to slip past Kizaru. Your own speed and skill still matters in that situation.

Meanwhile Busoshoku gives you armor and makes your attacks do more damage, hence why Luffy uses it with allot of his attacks, otherwise he wouldn't even activate it....