I'm going to pointedly disagree here. Five second cooldown on 75 second spell? Five extra gold? Very useful for getting that little extra farm you miss out on in the jungle. Amumu is actually a really fast jungler thanks to Tantrum.

You have very low MR on your 1st build, and dodge sucks anyway for Amumu, whose main source of damage comes from Tantrum and Despair.

Why bother getting AP if its only a single item? It barely helps.

Greed sucks, plentiful bounty is useless except for 5 gold, seeing Amumu jungle isn't that fast, no tenacity for Amumu jungle build.

1331 may be a nice number, but at level 8, you may want to consider nearly maxing out a skill instead.

Playing aggro for Amumu is really mana-costing, sudden surprise attacks usually work better.

Magic Pen is kinda useless when you play as a tank with no decent damage.

Hope it helps

Well i noticed that Ardor is not needed in the Jungler build so i went 1-18-11, even if 1-21-8 could be a possible choice. And yes... i don't have anywhere else to place those 3 points in the Laning Build, that's why they are on Ardor for extra AP.

For the second question: if i am jungling as Amumu i don't want to dodge anything because i need to be hit to decrease the CD on my Tantrum(E). The damage is not a problem thanks to armor runes. So because i don't want to dodge i don't have any other place to put those points in, so i use them for Strength of Spirit.

On both of the builds you have Amumu with Ardor, which provides a percent increase in AP and Attack Speed, but Amumu only builds AP in one of your builds. But I guess you don't have anywhere else to place them.

I'll also add, that if you sacrifice the buff duration increase you can have the final defense mastery. Also for the jungle, why have you got points in Strength of Spirit? With Amumu's low mana it doesn't seem like it would contribute to the jungling very much at all.