The difference between Non traditional and traditional swords is the amount of study needed. Most Showato a pretty homogenous, where as, nihonto need a tremendous amount of study. Not just for the smiths and schools, but how to tell a good one. Flaws abound in Nihonto (because they're handmade). Learning the different flaws and their consequenses can mean the difference of thousands of dollars. One may buy a Gunto with a Koto blade for eg $1500 But a realy good Gendai would cost over$10,000. Of course this depends on the condition of the blade and who made it.
Don't forget, Gunto are just Koshirae. One may have a very expensive Koto sword that is Gunto. Instead of a Generic Gunto term, one should differentiate between the blades. The only time the Generic term Gunto should be used, is with Showato and NCO.
Outside of Japan, we generally refer to Non Traditional Swords as Swhowa to. The Japanese use Gunto for these.
Outside of Japan, we refer to modern traditionally made blades as Gendai to. The Japanese uses Showato for these.
All the rest a named after their Periods ie. Shinshinto, Shinto, Koto. etc.