Building a new deck?
Even before considering any type of coating, the environment the deck is built in should be considered.
This will often indictate the type of timber that is used. Even the width of the board may play a considerable role in the installation and long term maintenance.
Why you may ask?
If close to the ground, the wider the board the more likelihood you will have of issues arising such as e.g. cupping from moisture absorption. Ventilation would certainly need to be considered, as does the method of fixing. It is also important to note that timber which is pre treated will also be corrosive to many fittings.
Do your homework and do things properly from the beginning and your deck will be a pleasure for a very long time.