Tank Mumu or Ap mumu better?
Honestly I think that tank
is better and if you disagree write why you think that it ap
is better than tank 
Honestly I think that tank
is better and if you disagree write why you think that it ap
is better than tank 
A mixture of durability and AP is generally the best option.
However, you always want to take Cinderhulk.
I like something along the following lines:

That said, I will drop Abyssal Scepter or Liandry's Torment for another defensive item if necessary.
I like your build but I still argue that runic echos is better early transitioning to cinderhulk late game if you get there.
I would argue the opposite.
Cinderhulk makes you far stronger in early skirmishes and ganks due to the added durability and sustained damage. While your burst damage is a bit lower, you can actually sit on people since you are too bulky to kill easily, letting you deal more damage over time.
Runic Echoes can be decent if you are snowballing hard, but Cinderhulk is far more consistent.
Well the issue I have with Cinderhulk is that the 15% bonus health is essentially useless early. On the other hand Runic Echos gives you a better clear speed, allows you to catch up to enemies and in my experience; if someone gets hit by an amumu ultimate early they are not tanky enough to survive the damage that it dishes out along with whoever else is in that lane.
I'm not experienced in Amumu jungle though it's jsut what I've seen work. However I do appreciate it quite a bit when the mummy can give me blue buff as a mana hungry mid because he's able to sustain his mana thanks to runic echos.
Honestly, I've not really been having any mana issues when I've taken Amumu in the jungle.
I find that Hunter's Potion and my jungle item are sufficient mana sustain when jungling on Amumu, so I can easily donate blue buff.
My preferred build is oriented more towards sustained damage (W-max, Cinderhulk, Rylai's slow) than burst damage, so I love having the additional durability.
I take Strength of the Ages and Scaling Health Seals, so I have plenty of health for Cinderhulk to scale with.
DAMAGE
My tank build for
is
