Technically:
An immersion suit is a thick suit with built in boots and gloves designed to be both waterproof and provide insulation. They are primarily provided on board ships and rigs for evacuation. They will keep you alive for an extended period if immersed, but offer virtually no dexterity. They are of no use to pilots
A survival suit is a water tight membrane suit, generally of breathable fabric which have built in socks and seals around wrist and neck. Insulation layers are required to provide protection from the cold. Worn by professional pilots who spend extended periods over the sea.
Dry suit, worn by divers, other water sports enthusiast and rescue services. Maybe breathable, but probably of heavier fabric than a survival suit. Sweaty and may restrict dexterity.
Wetsuit, insulated neoprene suit that allows water ingress via neck, wrist and ankles, but attempts to trap that water and allow it to be warmed by body temperature. Of little use in survival scenario since any wave action will tend to pump cold water into the suit.
THe best solution to the PLB problem is a PLB stowed in a pocket on the lifejacket belt, with its antenna clipped to the stole. Activate and will work without further intervention, ideal if you loose consciousness.