x265 is good for 4k stuff or 1080p if they used the the remuxes as source. If the media isn't source quality/remux, then there will be a loss of quality every time. Also, once you go x265, typically that file is done. It can't be changed to something else without a huge loss of quality.
Something like 95% of video files are x264 and have much better direct play support. If you have more than a couple users, you will notice much more transcoding. Just depends on your priorities.
So basically if you are storage poor and just need to save space, use x265. The catch is if you want best quality x265, you need source quality files, so you still have huge file sizes. If you want maximum compatibility and the option to change your files to something else later, then x264. It's all really dependent on specific situations for different people
It's a shame that most x265 groups microsize the releases or use the x264 as source what results in low quality releases. And the few groups that do use the correct source suffer from it.
That's why I created my own golden rule.
- 720/1080p => x264
- 2160p/4k => x265
- Don’t bother transcoding 4k
- If you cannot direct play 4k, then perhaps you should not even be collecting 4k.
- If you don’t have the storage space for a copy of both 4k and 1080/720, then perhaps you should not even be collecting 4k.
- To avoid transcoding for remote and non-4k clients, keep your 4k content in separate plex libraries.
- This may of course mean that you keep a 4k copy and a 1080/720 copy, but if you are collecting 4k content then you should not be worried about storage space, should you?