[MrForbes]

Aluminum is usually a better choice, as you can do more with it. An aluminum tube can withstand a very large load, and weigh very little compared to a solid wood board of the same strength.

Wood may be easier to work with if you have few machine tools, although clever design can get you very far with sheet, angle and tubular aluminum and a few hand tools. Rivets are strong, light and inexpensive. If you have access to a sheet metal shear and brake, you can make many aluminum parts that are strong, light, and rigid. As an example, we made a prototype ramp section that would weight less than a pound per linear foot, and can support 400 lbs over a two foot span.

Both wood and aluminum have been used very successfully to build airplanes, so it should be obvious that they both can be used to build strong, light structures, if the necessary design work is done.