All comes down to annual mileage and practical requirements.
I personally wouldn't use my V6 every day as too nice, too expensive to fuel and from a practical perspective it has none.
If you're doing 20k p.a. then Derv. is way to go, as a TS will need it's belts changing after 36k... One reason why I off loaded my 156 TS a couple of years ago.
147 & GTV are not comparable.
My advice get a JTD GT mate... Best of everything, very practical and very nice looking car too
Forgot to add...
GT diesel can be fitted with a Q2 Diff.
GT has the 147 dashboard
Much better seats than the GTV
Huge boot, as hatchback
I can comfortably sit in the back of my mates GT
Even has a cup holder!!!!... A practical miracle
You'll get up to 600 miles on a long haul.
Plus, you still get the Coupe look.