It’s one of those “it depends” things. You need to play with the quantity, temperature and time depending on the beans you get. If the beans aren’t freshly roasted, you really notice the difference with plunger coffee – it’ll taste flat or stale. In general, the more bitter flavour components take longer to come out. The longer you leave it in the plunger, the more bitter the coffee will be.

I hardly put any milk in my coffee, so I don’t like stuff that’s under-roasted. It needs to be roasted dark enough that it doesn’t taste acidic. (It isn’t an issue if you’re putting more milk in your coffee, because the milk acts as a pH buffer and you won’t get that acidic taste. A flat white or latte is far more tolerant of a light roast.) But if it’s roasted too dark, like a typical French roast, it just ends up tasting bitter.

I don’t make espresso, so I can’t compare how much coffee it actually uses. Espresso tends to need to be stronger as it is often used in milky drinks. Plunger coffee is often ruined by using water that is too hot, it should cool a little from the boil as the hotter water extracts more of the bitter flavours. Different styles of beans and roasts also work better for the different methods - espresso tends to focus on dark roasts, plunger and similar methods tend to favour lighter roasts and more subtle variations. Some of the difference between them is just what you are used to and looking for - a bit like with wine you can’t really compare a rich high-tannin red with a more delicate fruity white. They are both good in different ways.