I think it's a case of horses for courses. My Panda MJT has, for me quite adequate performance. Although its 0-60 acceleration isn't startlingly better than some other 1.2/1.3 petrol engines, the extra torque is really useful for overtaking on rural roads and on fast single carriageway roads, it makes relatively short work of overtaking slower traffic. There's little point in getting involved with fast cars, but then it was designed as a city car, although it can make reasonable progress on these roads and still return 62mpg. If you want more outright performance, then you are probably looking at a bigger car, e.g. a Bravo, in which case the 1.9 MJT puts forward a good case for brisk overtaking with good economy. If you try and put this engine in a GP, that's a lot of weight to put in the front of a small-ish car. Comments from owners of 1.9 GP owners welcome. A 1.6 MJT may make more sense in this car. If you look at 180/190 bhp larger cars, then the performance comes at a relatively high price in fuel. In those cases, the twin turbo MJT must come into its own.
A 1.6 MJet may well be a good option in the future for the GP and It'll be interesting to see how the model range changes through development. Thing is even though the 1.9 unit is quite big the Sporting MJet drives brilliantly. This, I think, is the fact that the GP isn't actually 'that' small (Bravo isn't that much bigger) and in many ways this engine suits it very well. A good indication of is the difference between driving the GP T-Jet with an obviously lighter engine....if you took the two cars and drive them back to back, as I did when deciding to buy, you'd be lying to yourself if you think there's any change in the overall handling. The MJet only has 10bhp of extra power and it feels like a more confident and mature drive thanks to the big lump. This might be the large amounts of torque available of course.
Call me old fashioned but I still don't think, as engine technology stands right now, there's a substitute for cc's. I know that the GP Abarth will adopt the 1.4 T unit but I'm personally a little disappointed about this as may well fall short of it's direct competition as a consequence. But, not totally sure, I think they're putting a 1.8 in the SS version which would prove my point I guess