Board Thread:Theories and Speculation/@comment-31611719-20170514123545/@comment-734582-20170515191349

TSB's are superior in offense and defense. PS is also a big target, whereas Madara's Jinchuriki profile was pretty small (namely, human-sized).

We've seen with e.g. Naruto that the Biju chakra heals, whereas the Sage chakra makes you more resilient. So it seems to me that by keeping his chakra for himself in stead of manifesting it in a huge susanoo, he benefits more. Couple that with TSBs fulfilling the offense/defense function better and susanoo being huge, i don't see the added benefit.

I do however see the additional cost: Susanoo would still be a jutsu to maintain (whereas TSB's seem free), chakra to invest and would make him a huge target whereas his TSB's were fulfilling his defensive and offensive needs. Considering Madara even survived Guy's worst, yet we've seen Susanoo break to lesser attacks, i think he made the right call.