Garden furniture has a lot to do with climatic conditions, so living in an area that actually gets all four seasons including rain, wind and a lot of sun in the spring summer and fall I do not know which would be the better choice for my new garden furniture. Of course wooden garden furniture is always nice because you can paint it to match your home decor of your back decking. With the right paint and stain hardwood garden furniture can also be water proof, although after a year or two it needs to sanded and re-stained. I must add that wood garden furniture also tends to be heavy and difficult to store for the winter which is always something to think of. Home and garden furniture is always quite bulky.
Moving on to plastic garden furniture which is not heavy and can easily be stacked and stored for winter and tends to be on the cheaper side of other home and garden furniture for outdoor uses. With the lighter weight though you need to consider if you have a great deal of winds where will you furniture end up. It can be great for extra seating when needed and stay stacked up on the side for when you don't. Perhaps the best thing about plastic is that it makes really cheap garden furniture that is also durable.
Wrought iron garden furniture is great for long lasting and can also be painted to match just about anything. Just as other things your metal garden furniture needs to have upkeep but it tends to once a year to every other year. A stiff metal brush, hose it off and a good rust proof can of spray paint works great. Due to the weight it will not blow away but can still be stacked for tidy storage in the winter, but can actually still be used in the winter minus the fabric padding.