There are no cons for them unless you have isocynite poisoning.There are a few different primers for different things.Epoxies are generally used for a sealer over bare metal and tend to be a little soft by nature.Urethane primers are broke down into surfacers for filling and sealers for sealing off bodywork and the original finish.It goes on farther and I think there's a post under Tips a few months back that breaks them down.Lacquer primers are the ones to stay away from unless you're doing a lacquer job.
