Part of the liquidation of my ridiculous knife collection is to fund my love for nihonto. I now have three pieces in my collection: papered wakizashi (formerly a naginata) from mid 1500's, un-papered wakizashi (also formerly a naginata) from the late 1600's, and a papered katana from the late 1600's. None of them are in koshirae, just shirasaya (wooden handle and sheath for storage only), but each one has a very distinctive feel to them. Some people may feel some sort of bond with their grail Busse chopper, but holding something that was truly made by hand, has stood the test of time and given the condition, was most likely used in battle, is a different thing all together. The last thing I want to do is swing one into a cinder block!!! Are you f@!#@#$@$ crazy!?!??!
Now, enough with the cute Japanese words and spirit infused, soul reaping steel; lets talk about one major difference that has been touched yet (I don't think). All true Japanese antique swords have a zero edge that is sharpened by polishing the blade. As far as agility, finesse and a clean quick slash into someone's flesh, this edge is superior to the secondary bevel found on a Busse sword. This alone pretty much brings us to an apples to oranges comparison since neither is going to perform the task better than what the other was designed to do. One could argue that someone could simply put a zero edge (with the rest of the blade geometry remaining the same) on a butaniku and go for it, but again, against flesh, I don't think it will be as good as the antique. In the hands of a trained practitioner of tamishigiri, I believe the slashing ability of the antique will be superior. However, if the target was made of solid wood, concrete, brick, stone, adamantium, etc. and the sword was in the hands of a chunky guy with no finesse, such as myself, the Busse wins hands down. Remember, a slash is different from a chop.
I am still an amateur to the world of nihonto and if I need to be corrected here, please do so.