I've run an '05 Panda MJ for nine years and 92,000 miles and I have to say that, for the mileage, it's the most reliable car I've ever owned in the 40 years I've been driving....hang on, did I just say 40 years? Er, yes, I think I did. But it's the truth. Since 2005, apart from normal service items and a couple of batteries I've had to replace one pair of anti-roll bar drop links, a pair of brake discs and a handbrake assembly. The only noticeable expense has been when I had the camchain replaced and, while I was at it, the belts and (because it wasn't worth not doing) the water pump. I also had the EGR valve replaced at the same time as it was a bit clogged up by then, despite an almost daily 13 mile motorway run twice a day.
I think it's recently developed a wastegate issue, but I'll have to wait and see on that one. Being an '05 it doesn't have a DPF but I think there isn't a diesel car made today that doesn't have problems with that.
I may well change mine next year and, at the moment, the TA is looking favourite as it's currently the most powerful Panda as the MJ was in'05, and, I don't seem to be doing the mileage I thought I might do. Having said that, one of the issues the original MJ had was that it only generated 145nm of torque which the TA does now, so the midrange might be as good as it was in the diesel. The current MJ puts out 195nm so despite the extra weight the new MJ should be quicker still.
So for me, as long as the build quality is as good on the new one as the old model, I'd be a little caught on the horns of a dilemma between those engines and, at the moment, I feel the TA is favourite as apart from the lower initial price, it must be lighter at the front than the MJ which can only be good for handling and driven sensibly is probably not much less economic than the oily one