When I started 35 years ago, we didn’t have outdoor wicker or outdoor fabric. We furnished porches or screened rooms with awesome authentic wicker furniture. The fabrics were cotton. Today we have synthetic wicker and synthetic fabric but for the purist we still have the good old stuff. In a semi protected space you can consider either option. The virtue of resin wicker is in the direct exposure to the elements but on a porch with some protection from a roof either will suffice. The fabric however is a significant improvement due to its resistance to mildew and its tolerance of the direct application of bleach if necessary.