Outdoor planters make the most sense for anyone with a porch, patio, or balcony that feels a little flat and bare, the kind of space where you walk out, look around, and think it needs something but can't say what. They're also the fastest way to make a rented apartment balcony feel like yours without touching the walls. Where I'd pump the brakes is a tiny balcony with barely room to turn around, because a couple of big planters there stop being decoration and start being an obstacle course.
Think about what's already sitting in that spot before you add more. A patio with a bold tile floor or a brightly painted front door doesn't need a planter competing for attention, it needs something plain that lets the door or the tile be the thing you notice. Same goes for a deck with a lot of busy furniture, striped cushions, a patterned rug, string lights, whatever, the planter should settle into the background there, not shout over the top of it. A plain concrete or wood porch, on the other hand, can take a planter with more personality, more color, more shape, because there's nothing else going on to clash with.
On finish, the easy ones to live with are the quiet ones, terra cotta, charcoal, driftwood gray, off white. They go with almost any house color and they age in a way that looks intentional rather than tired. Glossy glazed finishes in strong colors look fantastic in a store and then fight with your siding, your trim, and the neighbor's fence all at once. Plastic resin planters that mimic stone are honestly fine, nobody's climbing up to knock on them, and they're a lot easier to move when you decide the layout isn't working after all.
Where planters genuinely fall short is drainage and weight. A gorgeous planter with no drainage hole is a slow motion disaster for anything but a fake plant, you're basically building a bathtub for your roots. And the big ones, stone, heavy ceramic, concrete, look wonderful until you need to sweep under them or move them for winter, at which point you're calling a neighbor or just leaving them exactly where they landed in April. If you're renting and might move in a year, that's worth thinking about before you commit to something that takes two people to lift.
A good planter earns almost no attention when it's right, it just holds the plant and gets out of the way. That's the whole job, really, and it's worth picking for that over anything flashier.