I'm want to make a dvd of 16:9 24pa footage and was wondering what the difference is between export from FCP 4.5 using quicktime and compressor. I want highest quality video. And what settings should I have dvd studio pro on?

Just export a reference molvie out of Final Cut Pro and open that in compressor and choose a preset that fits the length and format of your project, then import that mpeg file into DVD SP and set its aspect ratio to 16:9. Check out larryjordan.biz for more info.