Ionic silver is far better than Mess of silver, since meso has huge nanoparticles. Nanopartice range anywhere from 200 to 500 atoms per particle.
Ionic Silver only has 2 atoms per particle.
While I would use Ionic over nanoparticle silver because of the particle size. The smaller the particle the easier it will penetrate into the heart of any virus or bacteria.
Atom size particles are still smaller than ionic, ionic is still made with chemicals, while atom size particles is not.