I specialize in no access for equipment or no equipment allowed jobs Murph. Pay attention please. WHat may work for you may often not work for someone else ......
While Stephen has restricted acces for geological reasons ( I've seen the place he works, and while stunningly beautiful, it is some hard terrain) we in the old world have to work in the little space left between buildings in cities and towns that have been growing up over millenia with no over all architectural planning. There are still places in old towns here, where one can't get a US size pick up truck through the streets.
The big chippers that roam the States are almost never seem here. If we used them, we'd end up dragging the brush way too far, because the chipper would be stuck between houses.
The " Is the GRCS worth the money" and " I hardly ever use speedlines" discussions stem from the same thing, I believe.
If you work in wide open American suburban areas, your take on both will be radically different from that of an European arbo having to squeeze branches and trees down between buildings.
Skid steers and material handlers are rarely seem here for the same reason, and when I have a job that is an obvious candidate for a crane, there is usually no room for the crane.
Back to original topic, I don't use a Z-rig much, since our small 800 kilogramme Tirfor is so easy to use. It sits in a medium size backpack, so it is easy to get to the tree, unpacks and packs as fast as a Z-rig, so.........................!