Why pass video signal through processor?

May be not! Unless your TV does not have enough inputs to support your sources (dvd,ld,satellite,vcr etc)and if your prepro comes with OSD (on-screen-display) you may have to use the unit's video switching in order to navigate the unit's setup via OSD.

I don't. I run my DVD on component cables straight to the TV. The only cost is that I have to switch the video source on the TV, separately from selecting the audio, which I run straight to my processor. Shorter signal paths are always better, I say.

The only reason for running the signals through the processor is if you need to see those on-screen displays for adjustments / info., or if you do not have enough inputs on your TV. I personally run my video signals direct from the source, and use the PIP for the on-screen display. The way I see it is one less connection / one less good video cable set I have to buy...