From what I interpret (is this the right word? idk),
it's like water currents in mob grinder, but without water.
(And that fan in mods...)
I mean, a 1m x 1m fan can't rly push a ~0.5m x 0.5m x 0.5m silverfish, so this should be the same as a 1m x 1m x 2m zombie.
However, it does make mob farms much easier.
On the other hand, I think chicken feather is enough. At least feather has 1 more usage... Haha
I agree with the other two, however I'm not sure chicken feathers are hard enough to get!