Aside from the higher cost of a dry suit you are likely to spend more maintaining a dry suit, by fixing leaks replacing seals and possibly the zip in a couple of years diving than you will on buying a wet-suit.
Although suits are made from a wide variety of materials. Its often a choice between Butyl nylon or cordura tri-laminate, or neoprene.
A medium weight tri-laminate with a shoulder dump is probably the easiest dry suit to start with. Its more of a loose fitting overall. As such, I don't think the average person needs them to be made to measure. They have no insulating factor, and you wear layered inner suit clothing for warmth. Medium weight tri-laminates are normally very puncture resistant and hard wearing. They tend to have a higher drag factor in the water than a close fitting neoprene suit. I see some companies use the term "Compressed neoprene", I'm not sure if that product really exists and its not marketing hype for high density 3 or 4mm neoprene. Neoprene suits are closer fitting, they have an insulating factor that tends to disappear as you go deeper due to compression. This type of a suit will change its buoyancy factor faster than a tri-laminate. The thicker the neoprene, the greater its insulating factor but the thicker it is, the harder it is to control your buoyancy on multi level diving. You can usually fin faster in a neoprene suit, because there is less drag. This handy if your bucking a strong current to get to a shot line, etc. Movment charactersitics, turning, changes in buoyancy, rolls and movement will be a little quicker in a neoprene suit. Neoprene natural insulating qualites mean you need less underclothing. Generally neoprene is not so durable a material for a drysuit as butyl-nylon or Cordura tri-laminates. Latex seals cuff and neck seals are more often than not found on tri-laminate suits. They are better seal but not so durable. Neoprene neck and cuff seals are warmer though they often stretch a little after use and leak a little. Neoprene seals tend to last longer. It used to be a choice of a back zip or diagonal front zip. Though I'm seeing suits with front zips like the whites but I've never tried them. Diagonal zips tend to break more often than back zips, (maybe its just me) replacing drysuit zips is very expensive. Shoulder dumps can sometimes get blocked by the inner suit material with certain combinations its may be necessary to wear an arm band, I have used an off-cut piece of tyre inner tube. I like a 3 or 4mm neoprene suit it doesn't last as long as a tri-laminate but I reckon the reduced drag helps me fin further and if necessary gives me greater ability to fight against a current and also reduces air consumption makes it worth it.
