Which nebulite should I mount on my weapon?

Hola Southperry.

I was wondering which nebulite should I use on my weapon.

Currently I'm a level 190 Evan with level 60 ambition. My only skills with %ignore monster def. are Illusion (20%) and Blaze (35%).

Which should I use, 6% total damage or 21% ignore monster def.?

If you have no ignore DEF on your weapon already, I'd say get 21% ignore defence. I have an 18% ignore on my dagger and it helps out way more than 6% damage would.