How to choose the right bitrate, H.264 profile and level for Web Video presentation?
If you are looking to get the best possible quality, encode at the highest bitrates you can factoring file size / upload time. 

Regardless of what you bitrate you transcode at; nearly all streaming platforms - YouTube and Vimeo included, will re-transcode the files using their own settings for Various Resolutions. Youtube for instance will take a 1080 file and transcode it into 1080, 720, 480, 360, and 240 versions for people who have slow connections. 

Your original file on both Vimeo and YouTube will remain available for download later from your Video's Setting Page. I am not sure if you can make that public, but they do retain it if you wish to pull the file back at a later date.