I’ve driven a number of T4s and have a T5, so hope this helps. The T5 is slightly larger and feels the generation newer that it is (remember T4 was designed in the 80s). Check the height of any local car parks though, coz T5 is very nearly 2m where as T4 is 180something, For best economy I think the 130 is the way – it has the 6 speed box, which the lower powered 4cyl engines don’t.
The 174 flies, but wont drop below 30mpg without extreme provocation. Well worth the extra if you do long haul motorway work, but I wouldn’t bother for town and local runs. It can eat tyres.
Typically you’ll get more toys on a runout model and more problems on the first of a new series, but I dont know how this relates to Transporters.
Happy hunting