There's a lot of advice on the internet on encoding settings to apply to your video before uploading to YouTube (https://support.google.com/youtube/answer/1722171?hl=en,, ...). They say that not only will compression allow your video to upload faster but it will make it look better when played back on YouTube (an example of this is at 0:18 in the YouTube link above).
What I also read is that YouTube re-encodes any video that you upload (example: "Telestream Episode product manager Kevin Louden started by noting that YouTube re-encodes all video uploaded to the site" - http://www.streamingmedia.com/Articles/Editorial/Featured-Articles/Encoding-for-YouTube-How-to-Get-the-Best-Results-83876.aspx).
So the obvious question for me is if YouTube re-encodes anything that it's asked to upload, why should different codecs make a difference to final playback quality on YouTube? To get the best playback quality on YouTube, shouldn't I upload a lossless file and let YouTube compress it however it wants?
I don't care about upload time or file size, I just care about playback quality on YouTube.