Engine problems 1-series

Hi!

I want to buy a used BMW 1-series. After searching for common problems I find that many people have had problems with timing chains and valvetronic in the engines. The only thing I can’t seem to understand is which engine(s) have the problem. Some people say that it’s only the diesels (N47) and some say its the petrol engines (N46) and some say both.
What is all of yours opinion about this? If I could choose between lets say a 118i and a 118d, which one should I choose (reliability wise)? Should I even buy a car with any of those engines at all if I don’t want trouble?

Thank you in advance!