the rendering speed isn't likely to be improved much between apps.

that is a REALLY slow process. on my 2 ghz g5 imac it takes 3-4 hours to render a DVD, more if i make really complicated menus. it's a pretty processor intensive process, so the only way i know of to make it fast is put it on the fastest hardware possible.

i've never used any non-apple DVD mastering apps, so i can't say anything about those.