Everybody discovers this when they get their new Festool OF-1400 router, but I'll point it out to those who don't have it to figure it out.
Routing on an edge always leaves at least half the base off the stock making the router less stable. Add to that the higher center of gravity of a plunger like the OF-1400 and you can easily make a mess of that edge.
In this configuration, the pad is out nearly a foot from the bit! The added stability is amazing and offers a lot of control for guiding the router. On a recent project with a lot of a shaped profile requiring climb-cutting on material very prone to chip-out, I used this configuration to bump-route much of the edge; the little bit of climb-cutting I did was very safe and controlled as that long arm to the base gives you a lot of mechanical advantage.