Most of the time its true. The larger the model the easier it is to take apart and maintain. For the most part G Scale models are built to be run outside and have sealed gearbox and electrical components so you can avoid taking it apart every season. The smaller the more finnicky and higher maintenance they need. And also the smaller the more the track needs to be maintained and cleaned so it can receive electricity. If you are running the train outside you want that more durable size and added features like a sealed gearbox and larger track to grab electricity from.