There are a few major differences. CFL's (spirals) allow you to add more light per square foot, so are better for micro growing. If you have lots of space to work with, tubes would be a better option.
The other issue is that tubes can have the ballasts remotely mounted, while CFL's (spirals) have the ballasts integrated, and therefore will produce more heat per given area.
And to the above poster, the spiral design is not to allow for optimal use of light, but to fit in a standard light bulb fixture.