I did monkey knifers from 81 to 90.
The benefits are that it is very fast xp (over 200k an hour if you do it right, I was filling my festive aura with 5 mins to spare on most days) and that you do not risk dying as you take hardly any damage.
It makes reasonable money if you bank the items (about 1m from 81 to 90 if you can sell the knifes).
Compared to Pyramid Plunder, Plunder is probably better when you get over 91 otherwise I found it slower xp.
The main disadvantage of knifers is it hurts your hands. It is also very boring - I survived by watching/listening to stuff on another laptop.