I have a Bridal show coming up in a few weeks and I'd like to be able to use my PS3 to show samples. I know that the PS3 supports .mp4, but I can't seem to get Compressor to output them at 1920x1080. It only wants to allow me to export them at lower resolutions. Any help?

If your source files are already at the target resolution then you should be able to use either the Apple-->DVD-->HD DVD: H.264 60 minutes or Apple-->Formats-->MPEG-4-->MPEG-4 settings. (BTW "Mpeg4 AVC" and "H.264" are just two different ways to describe the same codec Mpeg4 Part 10)
The PS3 will also play mpeg 2 HDV as m2t (if you happened to be working from HDV.)

If I were you I would duplicate the Mpeg4 setting and manually change the pixel dimensions and data rate to your liking.