For a native speaker, the difference is clear. We use the present perfect for unfinished or 'open' periods of time: 1A - He has never traveled by train. 2A - I have never been to France. In these sentences, we're talking about a person's life experience SO FAR, so the situation could change. For example, if your friend suggests a trip to France, you might say 'Great! I'd love to go. I've never been to France'. The option for me to go to France is still open - so we use the present perfect. We use the past simple for finished or 'closed' periods of time: 1B - I never fell in love 2B - I never had a family A person who says 'I never fell in love' is perhaps an old man who is talking about his youth. If he says this, it's clear that he feels that the period of life when he might have fallen in love is completely over. Or a 50-year-old woman would say 'I never had a family', because she is now too old to have children. If the situation cannot change, or if we feel the option for it to change is no longer available, we use the past simple. We have to use a past tense form along with time markers like 'yesterday', 'last week' 'in 2005', six months ago, 'when I was a child', and so on, because these are finished periods. Sometimes we use the past simple when it's understood that the time period is finished. For example, if we're having a discussion about what happened at a party last night, this will be in the past tense because we know that the party isn't going on any more. I hope that makes sense.

"He has never travelled by train" is in the present perfect tense and implies that at no time in the past has he ever made the utterance that "this" refers to. You might say this in response to an accusation that's shocking to some degree: "You told some of my friends that you hated me!", "No, you're wrong, I have never said that". "I never fall in love" is in the simple past and implies that in one particular instance that is understood by the context you did not fell that way. "Did you tell Dale that you were going to wait for me on Tuesday?", "No, I never said that". Note that in both constructions, it's probably more usual to use the demonstrative adjective "that" rather than "this" -- why? Because it seems that these phrases would most likely get used in response to a particular point by someone else said previously, and so you want to refer to that particular point. It"s about the situation when we say it. For the first is present perfect, the tenses means that you have done/haven't done something, but it is possible to do again. And for the second option is a simple past. Based on the meaning of past is something that we did, already happened and there's no impact which the first option has the impact.

In Case B, the speaker subjectively defines the period of time the action took ( or failed to take) place as a finished one, thus Past Simple. He/she doesn't treat it as having an opportunity for the action to be performed any more.