Well, first you could view the EC4 as more or less PC4 x 10 …
With the PC4 you have 16x24 (384) cc controls available, with the EC4 you have 256x16 (4096) …
The PC4 is good, it does exactly what it says but it’s not meant to be more than just 24 ( very good and reliable ) knobs. You can change midi channel and CC assignment with the 16 setups but it’s not praticale to jump on the fly from one setup to the other as there is no visual feedback (you have to label each knob on the hardware itself with the stickers included with the PC4) and the knobs will no longer represent there curent value (even though there is a snap function ).
If you"re loocking for a simple bank of 24 fixed knobs it’s fine, you could use it with different setups for different instrument or device ( like one setup for levels in the octatrack, one setup for a VST etc. ). Changing setup on the fly is possible but a bit tedious and you’ll have to remember or write down all your assignments.
But if you want to map hundreds of midi controls to different devices/vst ( that’s what I wanted to do ) the EC4 is superior in every aspect. Visual feedback (name, number or bar), in-out midi communication ( no value jump ) 16 setups of 16 banks of 16 encoders that you can acces by a two button press action. And you have NRPN and puch button actions etc … It’s super flexible.