It is easier to build a concrete shower pan than it is to build a fiberglass shower pan. When building a fiberglass shower pan, set it on a concrete slope. If you are creating a concrete shower pan, this step can be left out. Even though fiberglass shower pans involve an extra step, it is easier to do the finishing touches on a fiberglass shower pan because they are pre-made for the purpose. A concrete shower pan, on the other hand, needs to be sanded to protect your feet while showering.