Here's a picture of my nook with it's still-undecorated walls. I like the square rug because it defines the space where 2 more walls would be. Extending that logic, perhaps a square rug would make your space feel too closed-in, especially if the doorway is narrow. In that case I would say go round or octagonal. The table is 48" in diameter, the chairs are smaller than today's chairs and the walls are 7 and 7.5 feet. Hope this helps.

In general, I think rectangular tables work better for more than four people. To fit more than four comfortably & have room for everyone's legs, a round table will get too big to easily converse, etc. I have found that when I'm at a round table big enough to fit 6 (or more), it becomes difficult to converse with anyone across the table b/c the table is too big (diameter) - you end up having to yell across the expanse necessary to accommodate more then four people. With a rectangular table, you keep the 42" or so of depth and even though you add 2' to the length for each extra person - you can still easily converse with just about everyone. For only four people, I think a round table works and I like them, but not for larger #s. Now, the particular style of table is a different issue. Trestle tables are a nightmare for anyone with long legs - I intensely dislike them b/c I'm always bumping my knees and shins on the bar that runs the length of the table. They're also uncomfortable for people on the ends b/c there's not enough leg room at all, as Chicagoans also mentioned.

I love round tables. IMHO, a round table must go in a square room (which yours essentially is). Most DR are not square, so round tables are less common. I would totally do a round 72" for 8-10. With leaves if you have more. ETA - re the above ... do you have other eating areas? I would not use a formal DR for dinner for 3 anyway.

Round tables from what I’ve gathered take up less space so I’m not sure why a 58” diameter would be too big, but a 72”x42” would fit properly. I think either would look fine and also laid out a 70x30 ruffly measured table, honestly I preferred the round and felt I had more space.