Let me get the dice rolling then, add to the confusion. I have a THP200. When people talk about short drives, that means severe conditions for the engine. Funny thing is that most, a big percentage, of the people, drive their cars in severe condition. For it not to be severe, you'd have to drive 60km each trip, and who does that?
So, in the end, everyone has their RCZ's driven in severe conditions, minus a few exceptions.
Myself, I do very short trips most of the time, sometimes, not even enough to get my engine to normal temperature. I live 5 to 7 minutes away from my job. Sometimes I go get my wife, she works 15 to 20 minutes away. Couldn't be much shorter than that for any car, specially an RCZ.
As "Obi-Wan" Verminator said, it's important to once a couple of months, to strech the legs of the car. Word is to do those 60 Km at 3000RPM at least, to achieve a nice engine temperature and oil well all those parts while blasting out the bad stuff. So as you can see, it's something every owner should do once in a while, regardless of the fuel type.
Concerning that, let it be known, diesel cars suffer a lot more from short trips then gasoline cars, mainly, because diesel is a lot dirtier than gasoline. If you put a good gasoline, with high octanes and cleaning adittives, you should do ok. One botle of STP for injector cleaning every oil change doesn't harm also.
Talking about engines, the Diesel one is considerated more reliable but that's not a given, as well, there are thousands of THP engines around the world that never had a problem, not even timing chains or whatever problems it's known for.
Using math to add variables, one reaches some simple conclusions.
Remap the car is very nice for the moment, but puts strain on the engine that's not supposed to work that way. So problems come.
Change exhaust, move or remove catalitics, puts strain on the engine that's not supposed to work that way. So problems come.
Using the wrong oil or not changing it by preventing on severe conditions (and we already established that most of the cars are in severe conditions) brings wear to the engine, helps carbon glue to it, and it's not supposed to work that way. So problems come.
Changing engine air filter to a "sporty" one that allows more air to enter the engine, puts strain on the engine that's not supposed to work that way. So problems come.
Not using the right engine coolant or not verify and change it every so many miles or kilometers, puts strain on the engine that's not supposed to work that way. So problems come.
And I could be here all night.
If you want to buy an RCZ, just think of this. It's an experience like very few. You need to be responsible, to love your car and give it all he/she asks from you, many times, before he/she even asks.
In the end, you need to treat it like cars should be treated, and the RCZ will never let you down.
Of course, you won't be buying a new one so be very carefull on the previous owners. Listen to their story, to the car story. Where it came, who used it, what was it used for, service history, accident history, everything.
If the guy is a racer, think twice.
If the guy is a tuner, think twice.
If the guy is a slob, think twice.
Get an OBD II reader and connect it to the car before you buy. See if any errors show up. If so, what errors. We are here to help. Don't be hasty.
As for the motorization choice, if you want a normal gasoline car, get an THP156. If you want a fast gasoline car, get a THP200. If you want a racing car, get an RCZ-R. If you want something to illude you into thinking you have a real RCZ, get a Diesel. (Just because you'll miss most of the thrill of constantly loving your car with a false sense of security, because the diesel is a real RCZ, just a different breed).
One thing you must keep in mind if you're not a wealthy person like I'm not too. It's an expensive car to take care of, specially if you ignore my advices. Brakes cost more than usual, drivetrains even more, timing chains also, tyres 19" are crazy expensive compared to the regular joe's 15" or even the 18" many RCZ's have, oil has to be specific and it's not exactly cheap, specially if you get one with leaks, change every 6 months. Spark plugs are all the same, basically only one brand but you should change them every year if you want your engine to last "forever", carbon cleaning can be quite expensive if you get one with such problems, etc.
So, when you decide to buy one, buy one expecting for the best but preparing for the worst.
One thing is absolutly for sure, it's a marvelous beautiful car to own, it's a fantastic and safe car to drive and it's a passion that will only grow on you because all the love you give to it will be returned many times on the road, when you park it, when you walk away from it, when you arrive back to it, when you turn it on again, when you wait for the engine to heat up and when you finally can hit the pedal and that turbo kicks in, with you spoiler opening without you seeing or just because you pressed a button, and that large chassis will become a racing kart on steroids. Remember to always predict other drivers because most of them don't think you gonna be right by their side in the second they took off their eyes from the rearview mirror.
But do it. Choose your car, follow the advices and do it. Even if it takes a little longer that you expected or think you can handle, because is trully an experience you won't forget. Ever.
I hope this helped.