Aspect Ratio Question

Sorry for such a noob question but I am creating an animation composition in After Effects CS5 that will be used in Premiere Pro in my photo montage.

I will be playing the montage through my laptop that can play bluray disks so it should be able to output up to 1080p (laptop screen is also 1080p). The projector that I'll be using is a Sharp XR-32X DLP projector and from the specs shown on the website, it can display up to 1080p as well.

However, the projector screen that is available is only 8x8 feet so it is definitely not wide screen. I wanted to create the composition in high def 720p but the aspect ratio will be 16:9, correct? Therefore, am I better off just making the composition as NTSC D1 (720x486)? I'm guessing that it is technically better to just create the project based on how it will be displayed rather than just the output off the projector alone?

Sorry if I didn't include enough information. I'm new to this stuff and learning on the fly but making good progress.