I don't like saying it but don't be so naïve as to believe everything a "sales rep" is telling you. They are probably not lying to you, but maybe the whole truth isn't told. We are going to walk through a type of product here and talk about the differences between these and Duradek.
These other products are good products, when installed to manufacturers standards and recommendations by an installer that knows what they are doing and has experience. The issue here is trying to be sure all of the above is what your getting.
Here is a product that is often refereed to as waterproof. There is nothing in this muti-layer system is waterproof other than the "top coat" or sealer. It can be made to look very nice. Some installers have the ability to make all kinds of cool designs and patterns that are very pleasing to the customer. The top coat or sealer is applied as the walking surface, the more you walk on it or drag your furniture across it the quicker it wears off.
This stunning home along the bench in Draper Utah had very nicely designed deck over a slab patio. The owner had even had recessed lights installer around the perimeter adding a very nice touch of elegance to the deck. I am sure entertaining out here was often, showing off the outdoor living area. Unfortunately it seems the design was the priority here and the thought about protecting their investment with proper waterproofing probably wasn't a consideration until near the end of the build.
What you see here are the different layers of the product used. First a metal lath (heavy duty screen) was stapled to the wooden substrate. According to the manufacture this is to be done every square inch, that's a whole lot of holes in the wooden substrate! This step is done to try and keep the wooden structure from moving or minimize it at least. After the metal lath is stapled down a cement, or stucco like mixture is applied often in several steps, this varies by manufacture. Each application needs to be done within the temperature requirements provided by the manufacture usually above 50 degrees during the entire curing cycle. Once these have been applied and properly cured the top coat or sealer will be applied. Since cement and stucco are not waterproof this last layer is the only defense against water intrusion. These can be done in different colors and designs drawing the owners attention to the appearance rather than it durability.
This type installation can be everything the home owner has wanted, BUT they also need to understand that these all have an ongoing maintenance program that requires the top coat to be re-applied every 1-3 years. These requirements again vary by manufacturer. As long as the owner follows these costly requirements then the warranty should be applicable if there are issues.
Too often the top coat is never re-applied and within 3-5 years there are soft spots on the deck or sometimes there are little rust colored spots showing up. This is from the water soaking into and through the cement / stucco materials and into the wood. The metal lath will actually do a really good job holding the deck together, without it the deck would fall apart.
There are many products out there that can be used and all have one like requirement; the installer needs to have been properly trained.
To any home owner I strongly recommend that you take a minute and do some research on the product being used and the installer too. Make and informed choice that will meet all of your needs.