yeah i have a 1080i 30" sony crt HDTV, i send it 720p as it looks much better. Apperently the 360 for 1080i just takes a 540p signal and upconverts it so you are loosing detail. and i could notice.
from teamxbox's vga cable review:
QUOTE
Curiously, the VGA cable does not unlock the 1920x1080 (1080p) resolution or any resolution near the WUXGA standard, leading us to believe that when the Xbox 360 outputs 1080i using the HD component cable, it only does the old 540p-upconvert-to-1080i trick. That has been my suspicion from the beginning and this certainly backs up my theory.
so if you have a 1080i tv then try both and compare i did and i could notice a big diffrence on 720p