Worth it for what?
Are you shooting feature length movies on your phone? I imagine anyone doing that needs all the storage they can get.
Literally everyone else does not need it. I have about 1 TB of data stored in iCloud, which is accessible from iPhone, iPad, Mac, etc. All of that data originates from the devices. iCloud optimizes local storage based on how you use your device. My Mac has 652 GB (out of 1 TB) used, my iPhone only 120 GB (out of 256 GB). They both see and sync with the same data.
So while my iPhone technically already has access to 1 TB of data in the cloud, it will never have that much stored locally, or anywhere near it. The best thing to do is look at the current used storage on your phone. Then purge anything you don't need. If what is left is 3/4 or less of your current storage capacity, get the same capacity.