We have seen some of their abilities and they seem to be pretty much equal. I'm sure they have trained together and according to the data books their dream opponents are each other. So i decided to do them a favor and make this thread.
Im sure their fight would not end in a draw. From what we've seen i believe Kotetsu would win. He does that feet chakra thing so he can avoid Izumo's syrup trap technique and he has that Conch Shell Mace which has many abilities. He is able to attack from the air with that weapon according to the anime.
We probably don't know enough about them to pick a clear winner. It'd be easier if one of them had been promoted to Jonin somewhere along the line, but unless that happens we have to just guess. I doubt they are equals, but their friendship with one another, lack of manga information and lack of development skills-wise over the years quite frankly make this a hard one to answer.
Better question would be how one of these guys might do against Iruka?