Depends on your tastes! Which will probably also depend on where you live.
Northern folk (sweeping generalisation!) tend to buy butters like Lurpak - usually stuff that's in silver wrappers. This is called lactic butter, as it's made with a bacterial culture. This comes unsalted or slightly salted.
Southern folk tend to prefer butters like Anchor, which is sweetcream butter, and is usually in greaseproof or gold packaging. Usually a saltier taste than lactic butter.