I agree with the first half of your post 100%. Although ion version is somewhat good, it doesn't work as well as colloid as you clearly explained.
Nano is not marketing. It is the size of the particle. Making nano particles is no joke. It's a very high tech process.
The second half of your post regarding production of AC vs DC--I have to plead ignorance as I don't know anything about producing it using voltages. I don't know any details about producing it--period.
But nano version has demonstrated the most potent killing power.