The only difference between the Ultra 4800 and 4802 that's listed in the Wiki is the 4802 doesn't have a USB port. Same processor, same memory, same Fast Ethernet connection.
Buffering can come from two reasons: slow network and/or the media has too high a bitrate for the processor. If you're streaming from the Internet, neither of those should be an issue, as it's rare to find anything on the Internet that exceeds 20 Mbps or so. The exception is streaming from a home media server, such as Plex, Emby, or a DLNA server on your home network. With UHD video rips, it's easy to exceed the Fast Ethernet speed of a wired connection with any Roku that has Ethernet.
My solution for that is using WiFi, but it has to be 802.11ac on 5 GHz to be faster than the wired connection. I have tested my WiFi on my Ultra 4800, and the Roku has a max speed of about 220 Mbps on a strong 5 GHz WiFi. I've also tested the Ultra with some fixed bandwidth video files, playing from the USB port so no network bottleneck. The Ultra begins occasional buffering at around 180 Mbps, so that's about the limit of any existing Roku device. My UHD rips average around 80 Mbps, with peaks around 150 Mbps, so the Roku can handle them as long as my server transcodes the audio to a supported codec like AC3.
Dan
Roku Community Streaming Expert
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