Another major consideration should be which materials the kitchen & dining chairs come in. You have several main options, each of which imparts its own style and function.
Choose a wooden chair if you're going for a classic, rustic or timeless style. A wooden chair gives a look like the furniture is handmade and is a classic addition to any home. It's common to find a chair in a variety of wood types, though rubberwood is a popular wood species used in chairs these days for its durability.
It's also common to see metal chairs, often with slat backing. Choose these for modern, casual or industrial spaces.
If comfort is your main priority, choose an upholstered style, which often has padding added. You might question whether having kitchen & dining chairs in an upholstered style is a good idea, seeing as it might be easy to drop something and stain them.
If staining is a concern, choose a fabric or chair that is rated as being stain-resistant. For instance, it's common to find chairs upholstered with polyester, which is a durable fabric that can be more stain-resistant than, say, velvet.