Pine cabinet doors are a less expensive option and can last awhile, but they start to show their age easier than hardwoods. Having kids can also play a significant roll into what you choose. You don’t want something that dents easy and you want to be able to clean it with less effort.
Medium-density fiberboard (MDF) cabinet doors are made of densely glued fibers and covered with a material to look like wood. If your budget is tight, this may be a good solution. However, keep in mind that they may experience more wear and tear over time from exposure to moisture, grease, and other elements.
Particle Board and Plywood can be used for backing your cabinets as a cheap alternative to more expensive wood.