Portfolios are for protecting, carrying, and presenting works of art. Choose your portfolio based on how you plan to use it. Do you carry supplies and equipment in your portfolio, as well as finished works of art? The portfolio that's best for a job interview or client presentation might not be suited to the wear and tear of everyday use.
Presentation Cases are different from portfolios in that they contain a ring binder and sheet protectors, but similar to portfolios in that they have zip closures, and often handles as well. They are designed more for presentations than for transportation, so they aren't available in sizes as large as portfolios are. A presentation case typically comes with several sheet protectors, and it may have the capacity to store more. Additional sheet protectors, compatible with the ring mechanism, can be ordered separately.