If its only small journeys you would be doing then yes you would kill your dpf filter in no time at all on modern cars. petrol would be the way to go. All cars have the potential to be unreliable though don't they? it all depends on how they're looked after really. I have had a big V8 BMW 550i M-sport which was better on fuel than my 370Z but it didn't float my boat for long lol...But a great 4 door car with power when needed of course
I know that feeling well, when I was looking for a weekend car/toy, I look at loads of different cars but I kept going back to the 350Z. and now I am on my 3rd Zed.