I may be the outlier on this topic - I have both and each has their pluses and minus -
For Plex - to get the best experience with loading more than just video and HD Home Run and managing your portfolio of data you will want to use xteve software which will permit you to do all the same things that you can do in Channels DVR with a lot less hassel, and a one time membership fee to be a lifetime member which means you will have a price increase.
Channels DVR is a great service, I love the fact that you can use the "skip commercial" feature which Plex does not have perfected. It does a much better job of using third party streaming providers albeit I will never understand why someone who has YouTube TV would ever want to be add an additional fee every month or an annual fee if you pay for 12 months of Channels DVR when YouTube TV has all the features you could possiblly want right it their own application. Unlimited DVR, pause, rewind and record. That said you are an IPTV user this is without question one of the best platforms for IPTV - but keep in mind, with xsteve you also have the exact same features with Plex -
Conclusion - I prefer Channels DVR overall, after using it for the last 10 months, but I am concerned a pricing increase may be around the corner, and if it does I will drop it and stick with Plex because I already have the lifetime membership and both servers on line, for me it would be a quick pull the plug ordeal. I am ok with $60 year but will not pay more.
Good luck hope this helps and you have been enjoying the services if you have already joined.