The rectangular tables are the most common, which shows that they are a practical, functional and comfortable option. They are perfect for elongated dining rooms and they allow for more diners in less space. In a small room, a rectangular table can be shoved against the wall and still be perfectly practical.
Dining tables and chairs absolutely need to be proportional with each other, as there's no use in having a low table and tall chairs! For a pared back, organic and very zen installation, Japanese designs can be looked to for inspiration, with tatami mats housing a low table and numerous floor-mounted seats. With back supports in place, comfort AND relaxation will be combined to perfection.