This really depends on the details of the object, and what you want to reference from the scan. Reducing faces may remove features that affect dimensions.
Its possible to split up objects prior to importing into SolidWork so you you would not have to reduce as much.
For example, you could have an object with 60,000 triangles and split it into 4 sections with approx 15,000 triangle. Meshlab, if I recall, does not have a split function that will work on surfaces. Its possible to use a boolean subtraction in Meshlab, but your scan will need to be watertight solid. Blender (free) may give you more flexibility to split up your object.