STL files are essential to 3D printing. An STL file is what you can export from your CAD software to proceed with the 3D printing process. Most or all 3D printers read the surface of the STL file to produce its geometries. Whatever your computer and CAD software capabilities are, exporting an STL file with the highest resolution will give you better surface finish and dimensional accuracy. In the past you may have experienced rigid surfaces or polygonal holes and thought you had a problem with the printer. In reality, 3D printers build exactly what they see in the STL, including surfaces and geometries. Don’t be quick to blame the printer if the surface looks odd. Be sure to refer back to the STL file first. If that isn’t the problem then your sledge hammer would be then next step -- I’m kidding!
If you find that working with the file is difficult because of file size, this is where instinct and CAD skills come into play. As a designer or engineer, you have to find a perfect balance of resolution and file size by adjusting the settings in your CAD software. Experimenting with the resolution will make you aware of what your capabilities are and help promote a quality model.
Related whitepaper: Don’t confuse resolution with accuracy