I always shoot 1920x1080i 25np AVC Intra 100 for DVD and make the master the same format, it always looks very good, I just let iDVD do the down conversion from my pro res HQ master.
I do the same thing, shoot in the highest quality possible. For us that's usually
1080 30P AVC100, but sometimes due to space constraints it's 720 30P. We let
Compressor due the SD DVD conversion.
Ed
I know this is an old thread, but my 2 cents is to shoot in DVC-Pro50 widescreen. I don't want to have to render HD down to SD if it's a small budget shoot that will never need to be delivered in HD. I don't have the time to worry about reframing from an HD master. Just shoot it right the first time. The 4-2-2 of Pro50 can't be beat, and there is no conversion needed. Rendering to DVD is very quick.
I haven't timed it, but I don't believe there's much, if any, difference between sending an HD or SD file to Compressor to convert to MPEG-2 for DVD. I haven't shot anything in SD in years. A kids talent show may not be the best example, but I think shooting in HD and downsizing looks better than shooting in SD to start with.
Ed