The 30 gallon rigs are cheaper, usually. You can run a normal water heater on 120v with the stock elements, and have longer lead time to hot water, and need not pull large wires.
And if you really only need 10 gallons, disconnect the bottom element and run just the top one.
wrap some R-19 fiberglas around the top and top half and the thing won't add much to your electric bill.