1080i will give the best picture and most resolution.
just like dvds are 480i and the player adds progressive scan to give you 480P.
Your TV will add progressive scan to give you 1080P.
If you use 720P you will loose quite a bit of resolution, providing your source is not overly compressed, i.e. some Direct tv and cable HD.
But as always try both, as all displays and sources can be different from the norm in certain unique situations
just like dvds are 480i and the player adds progressive scan to give you 480P.
Your TV will add progressive scan to give you 1080P.
If you use 720P you will loose quite a bit of resolution, providing your source is not overly compressed, i.e. some Direct tv and cable HD.
But as always try both, as all displays and sources can be different from the norm in certain unique situations