Readers like a chance to work things out for themselves and infer meaning. By favouring showing over telling we give the reader a chance to build their own story within ours. As with any aspect of storytelling we have to find a balance within our writing but nobody can tell you what that is, you have to find it yourself by experimenting and finding your own style.
While I can’t tell you what your own style is it can be very difficult to pull off all showing or all telling. This is because, while the reader doesn’t like being told everything, they don’t tend to like a complete lack of concrete facts either. This is part of the reason why arthouse films can divide opinion so drastically, a lot of arthouse films are very focused on the visual element of film with very little explicitly stated, particularly common are subplots with no explanation at all, everything implied. Some people argue that you have to ‘work hard’ to find the meaning, unfortunately this is also often bandied around as if this is some great intellectual feat and not wanting to ‘work hard’ for meaning makes someone less intellectual. This isn’t true. People like different things and a story with everything implied isn’t necessarily a more beautifully crafted story than one with lots of telling.
When we say telling it can mean a lot things from saying what a character is like, to what they are feeling, to the way we relate past events. When it comes to past events it can be particularly tricky: Do we have a flashback? Do we imply the history? Do we tell the reader the history?
Some people will say you can’t have flash backs but once again this is subjective, a flashback can be an effective tool when it fits into the narrative but too many flashbacks can fracture the narrative and make it difficult for the reader to follow the story. Flashback does have the advantage that we can take a reader back into a moment and show them what a character was thinking and feeling in a way that isn’t always possible when we simply relate what happened.
Implying history between characters through their actions can be fun and interesting. It allows readers to build a story in their head if they’re wondering whether two people had an affair or what happened to break up a friendship. However, too little contextual history can frustrate readers and make it difficult to track who’s related to who and in what way. This lack of contextual history can also frustrate a reader if it is something that may have a huge impact on the interactions of characters in the present. For example, character A may seem perfectly likeable to a reader and character B’s dislike of A might appear completely irrational. It may be that in the past A committed a crime against B that makes B’s hatred for A completely justified. In such a case an implication that something dreadful happened in the past might not be enough to satisfy a reader, they might need to know what that something was to better understand the relationship.
Reasons such as these are why it is generally best to use a mix of showing and telling to help the reader better enjoy the story. I know I keep going back to the metaphor but writing is like giving readers a jigsaw; enough pieces and they can fill in the blanks but not enough pieces and all you’ve got is unrelated corners.