This is an interesting post and covers different types of excavators, so let's take them one at a time?
First let's discuss the most interesting design? In my opinion they are the machines like the Hydromac in your second post in this thread. It is basically a crawler dozer/loader undercarriage with a rotating upperstructure resembling a loader, but with articulated arms so it can sit in one spot to dig and load. It is in the same group as the Benati Multi Works 140 (there was also a later Multi Works 180), Tellus 125C and Bucyrus-Erie 60-S (which has a different style of undercarriage). Here's a short video of it in action:
https://www.youtube.com/watch?v=xg2bmYRVel0
There are also machines like the Colmas 170H which are just a crawler loaders (no articulated loader arms) with a turntable giving them the ability to rotate. There was also a red and white machine like this I have seen photos of, but I can't remember if it was from CMC or Yutani. Somewhere I have a photo, but no time to look for it right now.
Machines like Yumbo 35 and Simit SL9 are conventional hydraulic excavators in my opinion.
The articulated Mecalacs are their own breed.
For what it's worth; I'm searching for original brochures and catalogs on the Benati, Hydromac and Tellus machines for my files. Can you help me with this search?