they really are differnt from what I've seen, cutting oil is closer to gear oil, then it is to motor oil, and you don't want to use motor oil as a cutting oil because it can't take the presure, it just doesn't work well, however, like I said befor, some of the sulfer compounds in gear oil are not compatible with the bronze bushings in a Honda (and other) tranny, and they will attact, and destroy them, really I'm a little confused as to why honda chose those metals that would lead to them needing motor oil in a tranny, if gear oil would last longer, other then it being thiner, and I supose Honda did start out making motorcycles with a gear box connected to the crank case, so they shared oil.
In my rabbit I switched to Amsoil gear oil and that made all the difference in the world in cold weather - couldn't get out of first gear when it was cold - shifted like a summer day after. Use what the manufacturer calls for for the type of oil the use a lighter grade or/and synthetic - bearings and load surface area determine the weight of oil needed in the design of the transmission.
A pdf on Redline's website confirmed this by helpfully stating the gear and engine viscosities. 75W90 gear oil is similar to 15W40 motor oil, but the GM/Penzoil Synchromesh is actually closer to 5W30 motor oil viscosity.