That particual make/model I couldn't tell you.

But in general there's only really 2 ways to kill a turbo,

Either something gets in and wrecks the impeler which I have to admit I've only ever seen once.

Or the normal lack of oil changes.

Or late oil changes.

I can not stress this enough.

Oil starvation from old oil or low oil levels can account for almost EVERY turbo failure.

So turbo death is the owners/driver fault.

And given the cost of repair on any common rail diesel if you don't really do moon flight milages they're just not worth the risk.

And given the price of fuel I'd go for petrol.

If the running costs aren't the issue and its performance you're looking for, then the petrol engined car will likely be more reliable. If you are doing significant annual mileages (more than 20k - 25k miles), then the diesel would be far better, as long as its serviced on schedule and as others have said, consumables such as oil etc aren't scrimped on and kept nicely topped up.

Mazda has had problems with their diesel engines in general as many other car manufacturers have - see the 'Good & Bad' section of the car-by-car reviews on this website for details, but often so many diesel-engined cars' problems are associated with poor buying decisions, i.e. people buying diesels who do low mileages.

Its not just below the 20k - 25k miles as the approx. cut off point - that's a 'moving target' which depends upon the relative price of each fuel and the cars' purchase price - essentially the 'payback period' over an average car lifetime, but also people doing way less than 10k miles p.a. or mainly town driving over short journeys, which significantly contributes to the engines gunking up as well as not giving anywhere near the fuel efficiency advertised (they don't get a chance to warm up - much slower than petrol-engined cars).

Some of these problems result in having to replace entire engines or other significant (very expensive) components, which many people buying diesels for low-lowish mileages/town driving conveniently forget - the chances of a big problem occuring for them (even if the car is well kept) is quite high.

The Mazda petrols are now 'against the norm', in that they are naturally aspirated (no turbo), so again, less to go wrong than a diesel. I've done low mileages in my mk1 Mazda3 1.6 petrol, and it hasn't caused any problems and have only had to replace general wear-and-tear items over the 10+ years of ownership.

As regards the new 3's 2 ltr (165bhp) version, it is a bit quicker than the 'standard' 2 ltr version, but not that much (see HJ's review) - it sounds like it needs to be ragged to get the max. performance out of it. With the standard model (less power, same torque) and the 2.2 diesel (much more torque than the petrols), they don't so much. if you do lots of motorway miles, the diesel may be the way to go. Check the reviews, and owner reviews first, but note that some diesel owners may not want to admit to buying one for low mileages and wondering why they go wrong in a big way.

Older diesel-engined cars (15+ years old) without all those 3-lettered acronymns faired far better on medium mileages as they had less to gunk up. No going back though I'm afraid. With all the recent bad press about diesels (including from a health pov), its likely than petrol-engined cars, and probably hybrid-petrols will become far more popular. The forthcoming Kia Niro/Hyundai Ioniq might be worth a look, depending on the type and amount of mileage you do.

Best of luck.

Check out HJ car reviews- all the info is there.