darui is suigetsus worst matchup due to the fact he stated he was weak against raiton. it all depends on whether sui has his sword, and if he can trap darui in water bubble by forcing him to attack him with taijutsu.
Darui mid difficulty. Suigetsu had the handicap of having a broken sword and with a good sword, I believe both have sword skills on par with each other. However, Darui's raiton affinity makes him the clear victor in this match up as Suigetsu's best move is countered by Darui's best move.
Suigetsu's kenjutsu is probably better than Darui's, since his brother is a 7 swordsmen member. But I think Darui just destroys Suigetsu in ninjutsu. Black panther vs water is just OP as we saw.