However, mapping them out might be an insurance issue and will likely be a legal problem if you are caught (unlikely but possible if, say, you were in an accident) playing with the emissions system.
T6.1 diesel vs T4 diesel,
You will never have a vehicle with a 'character'. If it changes at all from parameters, then you'll get a little orange light come up on the dash which means it'll costya.
Lovely drive. More like a car than a van.
Amazingly comfy driver's seat vs driver's seat that made me feel like a 150 year old.
Less fuel economy than a T4. (37mpg vs 45mpg on motorway run)
Don't get one if you are only doing short journeys as will clog up your emissions systems/DPF and a little orange light will come on and it will costya.
Even if you only do long journeys you will be delaying that orange little light coming on and, um, it will costya.
Can still easily get parts for T6 whereas some T4 parts availability were getting a little sketchy.
More fancy gadgets and software and other stuff to go wrong vs basic tractor that will keep going.
Pros - In T6.1 I can enter ULEZ zone and pick up family members from the airport.
Cons - In T6.1 I can enter ULEZ zone and pick up family members from the airport.
Age for age - I very much doubt any T6/T6.1 will be on the road in 27 years, and probably not that many in 17 years.
This goes for any 'new' vehicle though. Whatever you do - don't get a vehicle with a 'wet-belt' (ford) as there probably won't be that many of them on the road in 7 years!