At my job, I have encoded our sites videos for a couple years by using X-Media Re-encode:
MP4 1024x576 VBR 1500kbps WebM 1024x576 CBR 1200kbps
I never had complaints about quality or buffering, I came about with those parameters by trial and error. Now my bosses want 3 qualities, which are:
MP4/WebM 1280x720 MP4/WebM 1920x1280 MP4/WebM 3840x2160
I warned them that the last one (4K) isn't mainstream as AFAIK. They think everyone has iPhone 6 I guess and that tomorrow every device will be Retina capable. I simply need a solid reference I can show my bosses the extra time in downloading, uploading, and encoding 4K will be. I assume the best way to do that is by the numbers (bitrates most importantly), without even considering the other factors such as limitation of broadband/DSL/Wifi, mobile, etc. Thanks in advance.
To clarify my question a bit more, my company's server is PostGres RoR S3 to store media, and infrequent use of CloudFront due to our content may need revisions and CF's invalidation process is a deal breaker. So we don't use You-Tube or any third-party platforms as of yet. I'm the front end developer (you probably can tell by the way I described my company's server :P ). So we use HTML5 and a in-house video player we developed. No Flash, no HLS, etc.