The POS (piece of spandex) that hooks in place over the rear cargo area does its job of hiding any contents. Once you get used to doing the connecting/disconnecting, it's not too hard to do. One advantage of the window shade cover used in the Prius is that the cover is automatically stored without effort (I know, I owned a 2010). The POS can be folded and stored in the Cargo Net accessory (be sure to order one) or left dangling from the two forward hooks. The other option for the Volt is to purchase a Volt Shelf that connects to the two forward hooks and is suspended via two cords to the hatch lid at its rear. When the hatch lid is closed, the Volt Shelf is horizontal, covering the cargo area. When the hatch lid is opened the Volt Shelf swings up with the hatch lid, exposing the cargo area.
Bear in mind, the Volt is classified as a Compact car, the Prius a Mid-Size car. But, don't let that be a show-stopper. Beyond that, the Volt is superior in roadability, economy, comfort and style. I owned a 2002 Prius and a 2010 Prius. I made two road trips in the 2010 and I have made two cross-country trips in my 2014 Volt. I averaged 50 mpg in the Prius and suffered a sore bottom and physical fatigue (from constantly correcting the steering to keep a straight line) at the end of each day of driving. The Volt seats are supportive and don't induce pains in the bottom or lumbar and the car tracks true and doesn't transmit bumps and road irregularities through the steering wheel. It's a heavy, solid car - a road car. In my last cross-country trip of 10,000 miles, I didn't bother to plug in to recharge the battery at night and relied on the onboard generator for the entire trip. I averaged 42.6 mpg. Had I been driving the Gen 2 version with its improved efficiency, I probably would have seen 46 to 47 mpg.