It all depends on how much mileage you do and where you drive most of the time. Diesel particulate filter failure is usually down to doing low mileages and short, low-speed journeys, which don't build up enough heat in the engine and exhaust to allow the filter to self-clean. 

 

So, if most of your mileage is long motorway commutes, then a diesel is perfect. If you mostly do short hops around town, get a petrol. 

 

As for Opel in general, they tend to be solidly built and reliable, but make sure you buy one with a full service history.