Re: Loss of quality after export from FCP7

As Sean said, try exporting with "current settings", forget QT conversion. Choose File> Export and use "current settings". If time/filesize are an issue uncheck "self-contained" to export a Reference movie, which is not itself a video file but it references your original media. It exports a tiny file very fast (I treat reference movies as disposable, one time use files just for opening in compressor and making files for Youtube, Blu-ray etc. Reference movies are NOT suitable for archiving or sharing).

Open the resulting file in compressor and apply the appropriate setting for YouTube/Vimeo in the "Video Sharing Services" folder. If you will be doing this often, especially if it is longer form video, I highly recommend Matrox MAX/Compress HD to accelerate creating the H.264.