The thing nobody tells you about chairs with arms is that half of them won't fit where you actually want to put them. A narrow desk, a tight spot by the fireplace, a dining table with a bench already crowding one side, and suddenly that chair you loved in the showroom is wedging itself under the table at an angle that makes everyone's elbows fight. Measure the gap before you fall for the look. That said, once you get the fit right, an armed chair changes how a room feels to sit in more than almost any other piece of furniture, because your arms stop having to figure out what to do with themselves.
They earn their keep in different rooms for different reasons. A living room wants at least one, something you can sink into with a coffee and not feel like you're perched. A home office needs one that swivels and holds up to eight hours a day, which is a different animal entirely from a decorative one. Bedrooms with a reading corner benefit from a smaller armed chair that doesn't swallow the space. And if you've got an open plan house with a toddler or a dog treating every surface as a personal obstacle course, arms actually help people get up and down without using the fabric as a handhold, which matters more than it sounds.
If you own none right now, start with one good upholstered armchair in a neutral that you won't tire of, placed somewhere you'll actually sit, not a corner that exists for show. Skip the occasional chair that's all shape and no comfort. A well built frame with a hardwood base and decent foam will cost more up front but it won't sag into a hammock shape within a year, which the cheap version absolutely will. I learned that one the hard way with a chair that looked sharp for about four months before the cushion gave up entirely.
Good ones age well. The fabric softens, the arms take on a bit of a worn patina where hands rest, and if you bought something with a removable cover or decent leather, it just gets better with use. Rotate cushions, vacuum the seams, keep it out of direct sun if you care about the color staying even, and wipe spills immediately rather than scrubbing later. The one mistake to avoid is buying on looks alone without sitting in it for a full five minutes, because a chair that feels fine for thirty seconds in a store can feel completely wrong once it's the one you're stuck with every evening.