Good post Jason.
The biggest advantage to redirecting the belay off of a higher piece is that if the second falls, the belayer gets pulled (slightly) in an upward direction rather than getting pulled (with more force) in a downward direction, potentially pulling the belayer off of his/her stance. I find it unnerving to get pulled downward when I'm belaying a second, so that is the main reason I redirect the belay. When I do a redirection, it is usually from a seperate piece that is not in the anchor system or I extend myself below the anchor and do a slingshot belay through the anchor.
Belay directly from the anchor using reverso-
Advantages: autolocking, belayer out of the system, no tug on belayer
Disadvantages: Can't belay the leader, so if swapping leads, need to move reverso to harness. Can be awkward if belayer is not somewhat below the reverso.
Redirect the belay-
Adv: tug on belayer is negligable and in upward direction. Ready for second to lead out.
Disadv: High force on piece used for redirect. Belayer is in the system. If redirect piece isn't high enough, can make belaying kind of cramped and awkward.
Belay directly from harness -
As the belayer, you should make sure there is little or no slack between you and the anchor in this setup. I got yanked over a tree branch and scraped myself up pretty badly once when my second fell and I had some slack.
Adv: Simple, familiar setup.
Disadv: Belayer can be pulled off stance. Belayer is in the system.