That answer depends on when you ask me.
I started with the standard polyfill but it didn't wick fast enough for me.
I tried the Pyramid tea bags (PTB) but that was way too hard to deal with.
Then I went with the blue foam and believe that it works very well.
But still I switched to the ADP mod with a spring and a plug of polyfill.
Using only a third of the polyfill as a plug solved some of the issues, so that was good.
I have now come to believe that the polyfill somehow interrupts the flavor of my juice.
So my plan is to try a blue foam plug with my ADP spring mod next.
But right now I am strictly dripping using my Direct Drip Cart (DCC) mod.
It may be awhile before I get motivated enough to go cut some pieces of blue foam for a plug.