Heating water: batch or circulate

I have a quantity of copper piping from removing an old hot water radiator heat system from my house in southern Ohio. I had thought to use it to make a solar collector panel. Building a panel and a differential temperature control system (to preheat water before it goes into the regular water heater) seems like a lot of effort compared to a solar batch water heater. Living in a temperate region (i.e., real winters and lots of cloudy days), I doubt I can use it in winter. Right now, I'm leaning toward scrapping the copper to pay for the batch system, since I think I'm limited to solar water heating for half the year or less. Am I headed in the right direction or is there a compelling argument for building the panel and circulating the hot water in my area?

Thanks!

Steve