The upper saw guard collection port works and works well. It must. We have never seen any sign of saw dust in Johns' shop.
Furthermore, I have worked with a SharkGuard installed and it does eliminate very nearly all of the saw dust that escapes from above the table. If that is the way you want to go, I do not believe you will be disappointed.
I, on the other hand, do not care for the overhead hose and all of the associated apparatus. That is why I do longer have a SharkGuard. Not that it did not collect the dust because it did. I did not care for the setup.
With that, I was left with the need to improve dust collection and I have done that. All I have to do is remember to connect and turn on the dust collector.
If interested, there are other threads that discuss the modifications that Mark (mbcabinetmaker) and I have made to improve below table collection. Think about it! The dust is created as the saw blade passes down through the work piece. If
adequately gathered at that point, there is no dust to be brought back to the upper surface.
This is but one.
http://www.shopsmith.com/ss_forum/viewtopic.php?f=10&t=6063&p=70071&hilit=dust+collector#p70071