Some parts for the 200tdi are now made of unobtainium like cylinder heads. The 300 is easier to work on - easier cambelt change for instance. It has a better oil pump and the head is easier to change as the motor is futher forward in the chassis.
LT77 gearbox is a load of rubbish IMHO, but I suppose you can get used to it until it breaks. I prefer a gearbox where you can get 3rd from 2nd occasionally
