It really depends on what sort of forestry and arb work one does. Dave and I mostly cut down mature trees. Dave does the ones the harvester can't easily process. I mainly work on an old estate with a bazillion acres on it, much of it untouched for generations. This sort of work is rather rare in our neck of the woods. So we both have to use larger, more powerful saws.
Now, in most places like the UK, they do not really use conifers to build with. It's for fencing, interior stairs, panels, and partitions, some furniture, pulp and that's about it. So they do not cut mature conifers as often as they do stateside in the PNW. And even then, most folks prefer hardwoods here. Since you don't have large conifers as a mainstay, you tend to go with smaller saws, and most folks are weened on these saws and techniques, especially arborists or folks working in cities that mostly do clean up and trimming. So when they run in to larger trees, they simply scale it up - a 14" 346XP is now a 20" MS440. Whereas with me and Dave, we have to scale down when we do the typical work most folks do on the islands. I use a 15" bar on a 38cc saw(Echo CS390ESX) and a 24 on an 044 and a 30 on a 288. These bars stay on these saws 99% of the time. The less bending this old man does, the better. I could certainly use a 36 on the 288 on occasion, but it's a pain to swing that thing around. There are several trunks I am working on that I could make do with a ported 395 with a 42+ bar on it.
All our saws are also modified. Which is somewhat rare for the Islands, and with ported saws being very rare.
This also transfers to how we cut. I was taught both the humbolt and the 'standard' cuts. But, I almost never use a humbolt on a hardwood unless I want it to fly off the stump and it's relatively straight, and I almost never use a standard cut on a softwood unless I want it to stick to the stump. I have never met anyone else on the islands using humbolts. It also makes it easy for me to tell if there's any poaching on the estate.
There is an accepted practice here on hardwoods, that mostly works, in that you make a small face cut with enough angle to let the trunk fall a good amount and break the hinge, and back cut a lot of the width in order to keep the tree from barber chairing. It's not as important on most softwoods, and definitely doesn't make any difference on smaller softwoods that are healthy. But the thing is, this is the first cut most folks on the islands learn, and it is the main one they use for about everything. It is slower, yeah. Oftentimes slower by about 3-4X as much time. But since it is mostly used on smaller trees, it's not as bad as using the technique in the PNW would be. In fact, most of what they teach here would be a complete waste in the PNW - it would take far too much time to put wood on the ground, and some of the techniques would bring wood in to the mill that would be unusable or need excessive trimming.
I also almost never bore cut unless it's a huge hardwood that could use a bit less hinge, or it if I need to be more creative for bucking big pieces of wood. Even then, I prefer to nip the hinge from the back if I can vs cutting into it from the front, which is standard practice here. That requires a longer bar.
Now folks on the continent that see larger conifers daily definitely use longer bars and more powerful saws in general. It's unlikely these are the guys giving out for PNW users with longer bars. Basically speaking, if a European gives out to someone for using a ported power head with a longer bar, it means they likely do not fall large conifers on a regular basis, and definitely not from a production stand point.
This is SGFoley in Germany using a 390 on a few decent sized Spruce. He generally uses a larger saw, and is mainly doing this video to show the capabilities of the little Shindaiwa, but this is a good demonstration of the European technique VS the PNW technique:
I did this to an oak I needed to leave the stump and roll off of a berm instead of kick back at me like it might have if I used a standard cut:
I cut mostly for firewood, so leaving a stump like this, which I'll cut off with the 044 or 288 later, isn't an issue. But if that was going to a mill, I would have tried to cut it closer to the ground.