Whatever size you will post to Vimeo or Youtube those sites will recompress it anyway.
Use a H264 or similar codec to encode it to a good quality and upload it there.
There are some good pages to guide you what to do for those kind of situations.
Youtube and Vimeo does have some guides
too.Like this but there are more:
https://vimeo.com/help/compressionHaven't looked for over 2K sizes but there are videos that are 4K so there might be a way.On Youtube at least...
Other then freaks like us nobody wants to download a 1 GB video that is only 12 seconds
There are Lossless codecs but i doubt that Youtube or Vimeo kind of sites do support them.
The middle ground might be using such a lossles codec and then using Drobbox or similar sites.
But then everybody has to install that lossless codec to watch it.
If you ask me make a high quality video according the best guidelines and put it on Youtube or Vimeo.
Vimeo encoding looks a little better to me mostly (not sure) and there is one option that i haven't found on Youtube;
users can download the original version from there if they want.