On the face of it, "standard" systems give you the most flexibility.
On the face of it, "standard" systems give you the most flexibility. However, if you are only planning to add Smarts to one part of your home or a specific task, it may be better to use a "proprietary" system. Some proprietary systems excel at the task they were designed to do - so sometimes choosing the best system for the job is the better way to go.