Unfortunately, those studies are not cited, as far as I can tell. Perhaps the manufacturers have the reference. Evidently, there is not consistent agreement on the filter size that is effective for viruses, although it would be hard to argue against the proposition that smaller is better. It's situations like this that just get my water boiling. Good thing I like tea.

I should have looked at the 2 models quoted a bit more closely before assuming either were typical backcountry filtering solutions. As it turns out both are somewhat unique to the market (something worth noting).

The Saywer model actually has a .02 micron filter which would put it in that ultrafiltration category the CDC mentioned.

The First Need unit is a bit different, it says it has a .1 micron filter but it could be one of its other stages deal with viruses (its literature didn't specify how exactly viruses were dealt with).

The EPA portion I believe refers to the EPA standards for water filter and purifiers; both companies say their products have been independently tested and have been shown to meet these standards. I found these standards described here.

Since both these products are designed to remove viruses (and therefore marketed as having the ability) they belong in a different class than the filters most of us would find at the local MEC or REI store.

The OP's question was on the comparison of water purification tablets and if one is really all that worried or concerned that tablets do not kill viruses then the water should be boiled. And like Hikermore mentioned, I also like my tea.

I'm totoally agree with you.You'r 100% good here that there is not effective agreement on the filter sizing that is effective for viruses, although it would be challenging to declare against the challenge that little is better.
I agreed what's said above!!!