Deciding whether to build your own custom closet storage unit or buy a pre-made closet storage system is going to depend on several factors such as cost, space, storage needs, personalization and, not least of all, your carpentry skills.
First, assess your closet storage needs. How many people will be using the closet? What quantity of clothing, shoes and accessories do you need to accommodate? What other items will be stored? If your needs are fairly traditional a commerical storage systems will serve your needs nicely. Otherwise, consider buildingy your own customer storage system.
Several national companies sell modular systems that can be configured to fit your closet space with options at different price points. But overall the cost of these systems will far exceed the cost of buying the wood and building the system yourself, assuming you have the carpentry skills. And you will still need to do the flooring yourself.
If you have a standard-sized closet, walk-in or otherwise, commerical systems can be installed to use the space efficiently. But since the modules are available only in standard widths, a very small or non-traditional space might be hard to fit. Again, building a custom system will allow you to make use of space that might otherwise be dead.
Commercial systems offer a variety of wood finishes, facings, moldings and hardware, providing a fair number of design options. Even so, they will have the look of a commerical system. If you are trying to match bedroom or bathroom decor, or otherwise want a custom look, you are better off building the system yourself.
If you are going to invest in a storage unit for your closet, take the time to assess your needs, your budget and your skills. The goal is to have afforable space for everything without clutter.