Liters is a measurement of how much displacement there is in an engine.
It is 100% impossible to say that 4 liters is better than 2, or vice versa, as it's only a measurement of air movement.
Typically, the more displacement you have, the more power you have. But that doesn't make it "better", just changes what it does.
Think of it like asking if someone 5'6 or 5'8" is better. Depends on a lot of other aspects.