720p or 1080i?

[HaHaUK]

Which do you use? And which is better in terms of quality on an LCD?

[mr_sockochris]

720p probably just shades it on an LCD as they're more suited to progressive sources than interlaced ones.

[sj33]

720p.

It's best to use whichever one closest matches the resolution of your TV. Given most HDTV's avaliable are 1280x720, 1280x768 or 1366x768, 720p is preferable.
Even if you do own a 1920x1080 set, you would still have to deal with the issue of 1080i being an interlaced format that gets deinterlaced (as LCD displays are Progressive), so it would be debatable even then, for gaming at least.
For films and the like, 1080i on a 1920x1080 display may be preferable as the source being of a Progressive nature isn't such a critical thing.

1080i for gaming is really designed for CRT HDTV's which usually support 1080i but not 720p.