QUOTE(osotogari @ Nov 25 2006, 11:40 AM)
my TV supports 720p and 1080i and it has an HDMI port.
Your tv doesn't fully support both 720p and 1080i if it's not 1080p capable as well. I'm guessing you have a flat panel (LCD or Plasma) so your best choice is probably 720p (well, I guess there's not much of a choice with PS3 games
). 1080i is just downscaled to 720p on your display, even if it can accept a 1080i signal.
If you can find a cheap HDMI cable (monoprice.com) I'd say go for it, and just set your PS3 to 720p.