Cement block is the most expensive, takes up more room but is far more durable. It is limited in how “nice” it looks from the outside. No insect issues (unless you put a wood roof on it) and very few water issues. Also, it is the most repairable should you run into it.
Wood framing is the least expensive and easiest to build. In wet or moist environments you are most likely to have insect or mold issues. This tends to be the most popular choice as it is the least expensive. They can look like anything and can match anything.
Metal framing. they are two types of metal framing: light gauge similar to wood framing but metal studs, and heavy gauge/ industrial. Light gauge metal is a bit more expensive than wood but you’ll probably need a commercial contractor to put it together as a lot of residential framers just aren’t familiar with the methods. Heavy gauge will likely be a prefab kit with several heavy members making the structural frame and metal panels infilling or skinning the structure. Light gauge metal looks like whatever you frame to look like (just like wood), but no insect and fewer water issues. Heavy gauge is a prefab tin can and looks like it. The manufacturer will likely put it together for you. Again, no insects and fewer water issues.
MKDesign 