Wooden garden sheds are definitely nice and I personally have one in my garden. On the other hand, it is often subjects to blisters and to problems of humidity. Aluminium and metal, on the contrary, are very durable and resistant, even if less attractive. And they don't need particular cares, unlike wood that requires more attention, for instance. In particular, I suggest to buy a metal garden shed since it is very light: so, you will easily carry it from the shop to your garden and build it, even if you are alone.