I shot an interview today with the Panasonic Gh2 at the highest quality possible and then brought it to FCP via Log and Transfer (Pro Res422) it looks great. What is the best way to upload to youtube and not lose too much quality?
I use an H.264 encode for YouTube uploads.
For the best quality set it to "Multi Pass" Quality to "Best" and Bitrate to "Automatic". If the file is too big to upload try and limit the bitrate.
Toutube supports full HD (1920x1080) but hardly anyone watches clips in this resolution -yet. So unless you want to be future proof I would go for a 1280x720 resolution for the upload.