If your tables will get heavy use, choose those with plastic- laminated tops. Side rails should blend well into the top of the table. Table sections should fit snugly together, with or without leaves in place. Slides on extension tables should operate smoothly. Chairs Need diagonal corner blocks with lag bolts that go into the back posts to give strength.
Decorative details add to the value of a piece if the rest of the construction is good.
Whichever type you select, look for one that has a smooth finish, with no streaks and no excess finish in the corners. Sit on the chairs. They should feel comfortable, sturdy, well balanced and not wobble or creak. Try to rock tables and chests from side to side. They should feel sturdy and not be easily overturned.