That is indeed fair enough - and its fair to suggest the US markets standard for "performance" is higher, because their light trucks have always been fitted with relatively powerful engines in comparison to trucks available from other countries.You make some good points. Back when your '88 was built none of the Japanese trucks put out much power; as long as they got to where they were going the customer was satisfied, and much fuel was saved compared to what else was available then.
The bar has been raised since then, and I guess my point was that Fuso should give us the OPTION of a larger engine, at least in the heavier GVW models. But maybe Mitsubishi does NOT have a larger, but still certifiable engine to suit the application. At least with Isuzu one has that choice. I just don't think a 3.0L 160HP engine will cut it in a 19,500#GVW truck, and that is what you are stuck with in a Fuso. Isuzu only puts their 3.0L in the NPR ECO model here in the states(can't speak for other countries). Everything else gets the 5.2L.
Performance (and comfort) was the primary reason I replaced the old Canter with my current F250.
Regarding your comment about small engines using more fuel at load - that isn't as true for diesels as it is for petrol/gas engines in my experience, consumption is almost 100% based on load and the efficiency of the engine itself. You have 2 engines of similar design but differing capacities, the larger engine with more cylinders will almost always use more fuel - even if its only slightly.