spruce did you used to work in the motor trade as you always seem to know your stuff!! 
Yes I worked in commercial sales with Citroen and Ford. Also worked for an Isuzu garage with the 3.5 to 7.5 ton category. Unfortunately, not being in the trade any longer means that I no longer have the latest information regarding new models.
One of the things that I found interesting is the performance of different engines in the same van over time. The Citroen Dispatch/Peugeot Expert/Fiat Scudo spring to mind. This model (as did others) came in 1.9, 1.9TD and then 2.0 Hdi (Jtd with the Scudo but was the exact same engine.)
The 1.9 non turbo was gutless, but could be very frugal on fuel if driven quietly. If pushed it didn't use much more fuel. It was a simple engine and bullet proof. The 1.9 turbo diesel was the same engine with a lower compression ratio but with the turbo added. It went like a bomb and when driven hard was fun to drive. Hated the turbo lag though. But it got through diesel like I couldn't believe. When that was replaced by the 2.0Hdi it became a different van. When driven sedately the fuel consumption was a little better than the 1.9 but not by much, but the performance was much better, especially with that 110hp engine. However, there was a big difference in fuel consumption between the 1.9TD and the 2.0Hdi - the Hdi was much better, even when pushed. That 1.9TD was a more aggressive power unit than the replacement Hdi.
The first van mount I had was a 1.9 Citroen Relay non turbo. It was replaced with my current vehicle, a 2.0hdi Citroen Relay. The performance is fine for me, far superior to the 1.9 but fuel consumption on average is higher on the Hdi because its easier to drive it harder.
In the early days no one would buy a Vito Van ( 1998 - 2004) due to engine and body issues. If someone wanted to trade one in, we didn't usually spend time on it as the owner wouldn't be happy with the trade-in price we could offer. But the same applied every where else. Even MB won't buy good stock off the trade.
The Renault Trafic had just been launched for a few months when the motor trade was warned to stay away from them as trouble. If you traded one in you had to have plenty of profit in the deal as it would go in comeback repairs. It didn't take long for them to get a bad reputation.
When you compare Ford Transit to the competition, the Transit is by far a better structurally built van, but they have never bothered to sort the rust problems out. As a spray painter recently said - its appears to be Fords and Sprinters built in obsolescence. The Transit Connects seem to do better with rot than the Transits do, but sills are something to watch as some do better than others.
My Son in Laws Transit Connect van originally was a van sold to the British army in Cyprus. It was imported back to the UK and sold. Could it be that vehicles destined to warm dry countries have less rust protection than others destined for wetter countries? Why protect again rust when a vehicle is going into the Middle East? It a costly addition that's not necessary. It just a thought. SIL's van has needed work on the sills. His is a 53 plate LWB with 57k on the clock.
Again the Tddi is a more simple engine than the Tdci replacement, but emissions dictated the upgrade.
