3240 is made of electric glass cloth soaked with epoxy resin by baked and hot pressed that board without bubbles and pits. 3240 is equipped with good mechanical property, outstanding arc resistance. In the medium temperature perform well its mechanical property. In the high temperature perform well its electrical property. Epoxy resin board is suitable for electric appliance and high insulation structural parts of electronic field. But its processing materials are halogenated that could  acts as flame retardant and release harmful gas such as dioxins with heavy smoke and smell which is harmful to environment and human beings. The most important is cheap.
FR4 is made of electronic cloth soaked with epoxy resin by high temperature and hot pressed that form into laminated board. The performance is better than 3240. FR4 is equipped with good insulation, dielectric, antiflaming and moistureproof that surface is smooth without pits and  standard gauge tolerance is suitable for high performance electronic insulation products. We can understand FR4 is upgrade version of 3240.
G11 has the best performance of the three. It is the one with high thermal stress is up to 288 degrees and its heat resistance value up to 160-180 degrees. The most outstanding is its low water absorption  which is the best choice with high voltage switchgear, high-end appliances, electronic products. But the price will be higher than the formers.