If you like videos about guitar sound engineering, I made a playlist about just that and added this video to it. As of today, there are 6 videos in this kind of format and I have outlines for 6 more. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-g3kTngQbQok.html
A 5th reason is so you can independently process the wet signal - for example, adding modulation FX (envelope filers, phasers, etc) to delays without affecting the dry signal.
The Blender I'm using in the video does not support stereo in any way. If you want basic analog routing and stereo is a must, you might need to look at some line mixers like the Samson SM10.
I think the only difference is that the V4 has an extra channel? I don't know, the V3 does the job nicely, but I wouldn't mind sometimes having an extra channel.
