The thing nobody mentions about lanterns is the smell. Not a bad one, just the faint warm metal and candle wax smell that builds up after months of actual use, the little tin ones especially, and you only notice it when you walk past the shelf on a day you haven't lit one in a while. That smell is how you know it's not just sitting there for show.
Where lanterns go wrong is in rooms that already have a lot of pattern or a lot of shiny metal going on. A lantern with a dark iron frame next to brass hardware on a cabinet, or sitting on top of a busy patterned rug, just reads as clutter instead of a nice glow in the corner. They want some plain space around them, a bare side table, a mantel, the floor by a chair, somewhere the eye can land without competing with six other finishes.
On sizing, the mistake I made in my own living room was buying one lantern thinking it would anchor a console table on its own. It looked lonely, like one shoe by the door. Lanterns almost always read better in twos or threes at different heights, a tall one and a short one, maybe a third tucked slightly behind. If you're putting one on a table, measure the table's longest edge first and don't let the lantern take up more than about a third of it, or it starts to look like the only reason anything else is there.
The difference between a good lantern and a cheap one shows up fast in the hinge and the handle. A well made one has a handle that sits solid in your palm with some weight to it, and a door that clicks shut properly instead of needing to be wiggled twice. Cheap ones have a tinny rattle when you carry them, the glass panes sit loose in their frames, and the finish wears through to bare metal at the corners within a season. Spend the extra there if you can, because that's the part your hand touches every single time.
Where they're the wrong choice is as your only light source in a room you actually read or cook in. A lantern gives you a pool of soft, uneven light, lovely for atmosphere, useless if you're trying to see your own stitches at ten at night. I learned that one the hard way in the bedroom and ended up adding a proper reading lamp within a month anyway.
I'll never not have at least one lit somewhere in the house by six in the evening, budget be damned.