If you build a constant circulation system there is no reason why you can't run it like a simple storage system. The difference is simply how you position the valves. You could run it as storage and simply use the piping to make filling and the rare draining and refilling easier. You could fill tanks with a garden hose and use the same hose to get it to where you want to use it but a piped system is going to be be simpler and easier once it is installed.

The difference in cost is little more than a few lengths of PVC pipe, straps, a couple of valves, and a few hours of fitting and gluing.