I will agree that particle size makes a big difference. The smaller the particles the greater the surface area of the silver and thus the greater the coverage. Think of a barrel full of BB's and a barrel full of softballs. The total surface area of the BB's is much, much greater than that of the softballs. And that is a pretty good analogy of the very best and smallest particle true Colloidal Silver versus just about anything that can be made at home.
The two true Colloidal Silver products I know of which have the smallest particle sizes are CureZone sponsor Utopia-Silver and Mesosilver - with particle sizes down to 0.65 nanometers or smaller.
Nothing wrong with homemade silver solutions, which are mostly ionic. My suggestion is to get some of the very best "just in case" something really tough comes along and then save money by making your own silver at home to handle everything else.
Myself, I keep anywhere from 2 to 7 gallons of Utopia-Silver 's Advanced Colloidal Silver - but that could be cost prohibitive for most people. I get the lifelong friend discount (the owner of the company has been a close friend of mine dating back to the second grade).