Wow this is daring! but
I believe current madara can defeat the sage of the six path,
I'll xplain,now madara can use both rinnegan and sharigan techniques and not to mention senju techniques+ madara can even do the susano'o without the sharingan,remember when obito rivived him he had no eyes but yet broke free from shikaku's sand sealing.
However on the part of the SO6P he does not have a sharingan jutsu all has is rinnegan (the power of senju and uchiha combined) which has not undergone evolution to yield other powers unlike madara's who had a sharinngan before awakening the rinnegan.
he just has a raw rinnegan and so can only use rinnegan techniques like nagato,this gives madara options more than so6p,therefore madara has the upper hand.
what do you think?