Surface vs. Solid Modeling

Computer Aided Design programs use surface or solid modeling to create geometry. Surface design is the predecessor to solid modeling, but they are derivatives of eachother:
Solids are really just surfaces that follow a set of rules enforced by the modeling software. This includes maintaining 'watertight' sets of surfaces, without gaps or overlaps, and differentiating the inside of the solid from the outside, (assigning a density). The modeling software is doing a lot of automated tasks behind the scenes to make all this happen.

Surface modeling has two principal advantages over solid modeling. The first is in the type of modeling when shapes must be constructed face by face. This is often associated either with complex shapes or with imported models that must be rebuilt or repaired face by face. The second main advantage is defined in terms of efficiency. In the solid modeling world, one often makes use of a solid swept cutting technique. This is a bad habit and is better handled using surfaces to manipulate the solid - hence a hybrid technique. Time is saved by not having to create an inclosed cut profile. From another view, the solid cut profile geometry is not set up to work well with the changes in the model, so they tend to create alot of rebuild errors and extra faces.

A consideration to make when selecting which modeling type, is IGES files, and how often you work with them. IGES files are can be generated by a Coordinate Measuring Machine, (CMM), and are neither solid or surface. Both modeling programs will usually work with the file becuase of their nature: points mathematically defined in a spacial plane. Problems arise in the nature of solid modeling rules. Namely, the 'water-tight' rule. Points will have to be converted into inclosed profiles in 2D planes. Once this is accomplished, a draft or loft technique can be applied to recreate the geometry. This is often a tedious process.

Solids generally take less time to create, but can take more time to regenerate when working with many redundant faces. If you rarely make changes, then maybe modeling efficiency should be your biggest concern.