There really is no ultimate material, although vulcanized rubber comes close.
Vulcanized rubber is tough to beat for over all durability and repairability. As indicated above it is quick and easy to patch - dry the leaky spot off, hit it with a tire patch and you could be back in the water in 15 minutes. It also usually has some stretch to it which allows a little snugger cut to the suit than trilam suits that do not stretch at all.
On the negative side, they can be quite heavy in the more durable commerical weights and the heavier weights are less stretchy. And they come in back entry models only.
Trilam suits are almost as durable and are a lot lighter and usually less expensive than a vulcanized rubber suit. But they have no stretch and consequently must be cut with a looser fit to allow full flexibility. This is particularly true with self entry models which have much more lenght in the torso than a rear entry suit to allow you in and out of the suit, whihc in the water adds up to a lot more bagginess. They are also slower to dry and repair than vulcanized rubber.
There are also bi-lam suits made out of polyurethane coated pack cloth. They work ok for a while until the urethane coating breaks down at which point they leak. And they are prone to seam leaks which are almost impossible to fix. They are affordable but are by far the least durable suits available.
Crushed neoprene is a nice compromise material with good durability, a fair amount of stretch, and they offer the potential for a trimmer cut without compromising flexibility. But they are heavier, slow drying and it is harder to find and repair leaks. They also tend to be quite expensive. It is another material that comes close to doing it all pretty well.
Neoprene suits are affordable and very stretchy which allows a very trim almost wet suit like cut. And the inherent warmth of the shell material allows you to use much thinner and much less expensive undergarments. In my experience they offer by far the best "swimmability" available in a dry suit and will tolerate less air in the suit than other types where the squeeze tends to be sharper and more painful.
They are also comparatively inexpensive at about 1/3 the cost of a trilam and a 1/4 the cost of a crushed neoprene or vulcanized rubber suit. They are arguably less durable, but I tend to get at least 400 dives per suit before they start to leak, and when you multiply that times 3, I get at least as many dives out of the three neoprene suits I can purchase for the price of one trilam as I do that one trilam, so it's a wash. And in the process I get three sets of seals, three sets of boots and three new zippers over the life of the three suits for "free" so maintenence is cheaper over time than with a trilam.
In my exprience in very cold water (32-35 degrees), they tend to be much warmer than a trilam or vulcanized rubber suit with heavy thinsulate underwear, even at depths to 150 ft. where the compression of the neoprene material should reduce the insulation it provides. I don't know why they are warmer, they just are.
The downsides of neoprene suits are much slower drying time, heavier weight (about the same as a crushed neoprene or vulcanized rubber suit) and rear only entry zippers.
If possible dive different types of drysuits and see what works best for you. What is great for one diver is not always the first choice of another diver. Unfortunately many divers start with one style suit (usually a trilam) based on what they read or hear from other divers and never try other types. Consequently they tend to have strong predjudices but often have no real comparative experience and do not know what they are missing with other types of suits. I know because I used to be one of them.
