Creative Composites takes the approach that the REQUIREMENTS drive the materials. These can be quantity, mechanical and physical properties, aesthetics, customer specifications or any combination thereof.  We have worked with multiple reinforcements, cores, additives and resin systems:

R-Glass Polyester Urethane Nomex Honeycomb
Kevlar (K29 & K49) Vinylester Epoxy Aluminum Honeycomb
Nylon Epoxy Acrylics Various Foams
S-Glass Urethane Methacrylates Balsa Wood
C-Glass Phenolic Thermoplastics Syntactics
Twaron Thermoplastics Silicones Mineral Fillers
E-Glass Polyurea Polyurethanes Tougheners
Carbon Fiber (various types) Fire Retardants / Smoke Inhibitors

In many cases, the requirements dictate the use of an epoxy resin for its mechanical properties and the only resin available is in prepreg form, but other factors preclude the use of prepreg.  In conjunction with resin formulators and manufacturers, we often develop custom systems to allow the resin to be processed economically while still meeting the other requirements.