Jungle Renekton: 21/9/0 Masteries or Not?

Is there any reason for me to take 21 offensive masteries on anyone in the jungle, let alone renekton? I just won a pub with 10/17/3 but after trying that out I'm pretty sure offensive masteries would work just as well. But I'm not entirely sure.

Essentially which is better: ~5% more damage to minions and monsters and ~10% more to champions, or 5 more starting armor, 10% reduced crit damage, more regen and 1.5% movespeed?