An empty tabletop is only part of the footprint
Do not compare round and rectangular tables solely by the surface area of their tops. Chairs sit outside that outline and move back when someone sits down. Make paper outlines of both candidates on the floor, then add the chairs you already own. A trial without chairs almost always understates the space involved.
Seats around a round table face a common centre, which can suit conversation in a small group. However, the arrangement needs room on several sides. A rectangle often fits a narrow recess more clearly. Pushing a round table halfway into a corner gives up some of the seating that made its shape appealing in the first place.
Include what happens below the top
A pedestal may offer more freedom over where chairs go, but its base can occupy space needed for feet. Four separate legs restrict how many chairs can fit between them. Check the clear distance beneath the top as well as the table's overall width, and note the height of any apron below the edge.
This matters especially if you already have dining chairs with arms. If they cannot slide under the table, the eating area stays larger between meals. An extra guest needs room for their legs and a place setting, not merely a gap along the edge. A quoted seating capacity is therefore a starting point rather than a substitute for trying the intended chairs.
Consider the jobs between meals
A rectangular edge gives a straightforward working position for a laptop or sewing machine. A round top can be approached from several directions, although a wide project may spread towards its narrowing edges. Set out plates, a serving bowl and the things that normally share the table. This reveals whether a compact size is genuinely sufficient.
If two people use the table most days and guests come only occasionally, let that everyday arrangement carry more weight. An extending model also needs a separate trial in its open position. Keeping the daily eating area accessible and making another arrangement for rare large gatherings can be more useful than permanently surrendering the main walkway to empty seats.
