What´s the fastest private proxy ?

You do realize it's not just the proxy that you have to consider here right? If you connection is slow to begin with, the proxy is only going to help so much. I know for a fact their proxies are much, much faster than what you've just quoted. If that's the case you need to post what your actual connection behind those is. You can try hitting them up and maybe getting a new list with some IPs that are closer to you, but if you're trying to use them on a 5 MB/s line it's not going to upload like you want no matter what proxies you use.

Exactly, the main thing is your internet connection, in your case, to upload a video to youtube, the video then travel from your PC to the proxy to be upload and this will depend on your connection speed.