The moment a round table wins is when there are five of you and only four chairs, and somehow everyone still fits, nobody's wedged into a corner with their plate on their knees. No sharp edges to navigate around, no "head of the table" politics, just people leaning in. That's the whole case for round over rectangular in a lot of real rooms, and most people don't think about it until they've hosted a dinner that felt cramped for reasons they couldn't name.
If you're starting from nothing, go a size up from what feels reasonable on paper. A 42 inch round seats four comfortably, but the minute you add a laptop, a candle, a bottle of wine and someone's keys, it shrinks fast, so I'd push toward 48 inches if your room allows it, which gets you four with real elbow room or a squeeze of six for something casual. Measure the path around it too, you want at least 36 inches of walking clearance on every side, otherwise you're doing the sideways shuffle every time someone needs to get up for more ice. Wood tops develop a nice patina if you let them, little scratches and water rings that read as lived in rather than ruined, as long as you wipe spills promptly and use a mat under anything hot. Laminate and glass stay pristine longer but show every fingerprint, which is its own kind of maintenance. A pedestal base, one leg in the middle, is worth seeking out specifically because it means no one's shin is fighting a table leg, and it makes small rooms feel less cluttered since there's nothing breaking up the floor space underneath.
Round tables tend to suit rooms that are themselves a bit squarish or awkward, where a long rectangle would fight the walls or block a doorway. They're forgiving in open plan layouts too, softening a space that's otherwise all hard angles, counters and sharp corners. In a bigger house they can feel almost too modest for a formal dining room, which is fine if that's not the vibe you're going for, a round table reads casual and gathering focused rather than grand.
When it's delivered, check the underside of the top for how it's attached to the base, some cheaper ones use a thin center bolt that wobbles within a year of normal use. Press down on one edge and see if the whole thing rocks, a table that rocks on day one will rock worse by month six. Check the extension mechanism if there is one, and count the leaves, because missing hardware is more common than you'd expect.