I currently am using a Dell Optiplex 5040 SFF with an Intel Core i7-8700T & 32gb of ram.
I recently purchased a Dell R720XD with 2x Intel Xeon E5-2680 v2 2.8GHz (3.6GHz Turbo) 10 Core Processors - 25MB Cache & 32 gb of ram.
The Optiplex has been great hosting my plex, when adding media it generates preview images and detects intros a lot faster than the synology ds2419+ that I used to how my plex on.
Would the R720XD be worth hosting my plex instead or is the Optiplex better?
CPU wise , I prefer Optiplex. But R720xd will give you plenty of slots for storage expansion and more power consumption.