The torque produced by the v6 tdi is very linear, that's why it seems slow- max torque is between 1500 and 3200 rpm's, it has a very, very flat power curve which won't give you whiplash every time you change gear !
85 miles per day is a long drive and you do save a bit of money in the 1.9 Tdi. Now, the old rotary engine AFN/AVG/AHH,etc. returned great fuel economy, the new PD are far less economical. Just to give you an example: i have a golf gt tdi 130Bhp mapped to about 165 Bhp(also has a 2.0tdi turbocharger fitted: larger turbine and compressor wheel with small trim so it builds boost quicker), it does 200 miles for £50 worth of fuel- same as my 300 Bhp a6 quattro ! We are comparing nimble FWD with heavy quattro a6 estate and i don't drive it lightly at all ! The figures are round town with occasional drive on motorway... The a6 is more planted, much more grippy and accelerates/brakes better. It also has a better interior compared with the vw... Did i mentioned the larger engine is cheaper to insure compared with the 1.9 Tdi ?