If you have one formal and one casual dining space, you can really go to town with different chair designs for both. A casual spot will do best with sociable, comfy seating that naturally leads to conversation, whereas a formal setting is where you can play around with luxury fabrics. If you only have one dining room, you're going to need to combine all of these elements in one set of chairs, if possible!
If there is one essential element in the dining room, then it is without a doubt the table and chairs that we place around it. So when deciding what type of table we want for the dining room, there are many questions: What material should we use? For how many diners are we setting up? Which way to arrange it?