The advantages of 1080p are higher resolution and less scaling. The higher resolution only matters if you're close enough to be physically able to perceive the higher resolution.
This chart should help you determine that.
The scaling is very simple. If a 1080i signal is sent to a 1080p TV, then deinterlacing is all that needs to be done. If a 1080p signal is sent to the 1080p TV, then nothing needs to be done with the signal. However, a 720p TV (technically 768p) must scale everything since no source is 1366x768 resolution. On a TV with a good scaler, this might not be noticeable. On a 720p TV with a poor scaler, artifacts and other problems can be introduced from the scaling. On a 1080p with a poor scaler, at least 1080i and 1080p signals should be displayed well as long as the TV can deinterlace the 1080i with no problems.
I went with a 50" 720p TV, because I'm far enough away for the increase in resolution to not matter. I could've bought a 50" 1080p TV for the same price as mine, but the contributors to PQ that are more important than resolution (contrast ratio, color accuracy, and color saturation) were all better on my TV than on the same-priced 1080p TV; therefore, I chose the one with the better PQ. If I sat 6 feet from my TV, then I would've seen 1080p as a requirement since I would've been close enough to perceive the limitations of 720p. I sit 9 feet and do not perceive those limitations.