I use both (paid versions too). Soon after I started trying emby out, I completely switched over to it for myself. The main reason was that Plex apps kept transcoding all the time (every time I turn on srt subtitles, if there is multi channel audio, Plex transcodes). Emby apps direct play or direct stream on the same hardware with subtitles.
I still have family and friends streaming off of plex. I figured it would be too hard to switch some of them over as they are not very technical. So I still run both, but emby for me, Plex for the legacy folk