Hashirama wins this
--Once he goes SM he has the reflexes to react and dodge something as fast as FTG,,, meaning that kamui warp is not happening,,,
--Through the aid of Mokuton KB,,, Hashirama would have the diversions to disrupt Obitos kamui usage,,,and would allow the KB to attack Obito,, once Obito solidifies to attack one of the KB,, (whiich Obito wont be able to decipher),,,,,
--Hashiramas mokuton arsenal is perfect to counter against Bijuu,,,, he uses SS to overwhelm all of the bijuu and tank everything in their arsenal,,, whilst using the mokujin and myojinmon to restrain the biijuu,,,,
--Once the bijuu are down,,, Hashirama can use his flower tree world (FTW),, to bypass the 5 min limit of Obitos kamui,, and can attack him accordingly either during the jutsus interval,, or after the 5 minute limit