Both are important, but for different things. If the trip time is too long nobody will take the train. If the train isn't predictable nobody will take the train. You get a bit of leeway in different situations though. The longer the trip the less either matters because what else can you do? If you are only going a few meters it needs to be here now (whenever now is - on time in 1 minute is too late!), and it only needs to be faster than walking that distance. In between you get some ability to do things.

In the Swiss case on time is critical because they want people to depend on their next train being there when they get there. They assume most people will get off one train and get on another (or a bus) so they all meet in the same place at the same time. Early does nothing for anyone unless the bus/train they are meeting is early and leaves early. This is one good way to run a system. The other is run so many trains/buses that whenever you arrive there is another waiting for you that will leave as soon as you can get on. This second way to run a system is much faster and better for everyone - but the costs are significantly higher though and so nobody can afford to run a large system that way. (large cities often can run this way and should where they can). Note that system is the key word here. If you only have one train the considerations are different.