if i'm not mistaken , the engine gearbox & suspension is same in both EGG shape & the BOX model , the egg shape is slightly less fuel economical due to the body is heavier than the Box model. this is the reason why the Box model is also in the same price bracket as the Egg shape .
one of my very good friends owned a BOX model diesel 32- non turbo ( in very well maintained condition) & we went to ampara & back with A/C & it has done about 25km/ltr . ( i can remember touching 120km/h mark with 3 people in the car with A/C)
finally my friend sold it to a known person about 3yrs back & he is maintaining the car in the same condition .
my friend tried to buy it back recently , but the current owner is not willing to part with it. he says it was his best buy.
as far as i know also part are not a problem as there are lot of guys who get down things , & engine repair is not a major issue and it lasts about 70,000 -80,000kms with out a problem if maintained well . this is for the Non turbo.
but as everyone said finding a car which has less vibration, good body shape, & good interior is quite difficult as due to the fuel economy 99% of the cars are really abused.