An interesting possible future option for the Prius is upgraded batteries for better EV mode. See this link http://www.edrivesystems.com/technology.html

While the price is outrageous today ($11k+) it could/should fall over the next few years. I'm hoping that this system (or even better a system provided by Toyota) will offer a true EV mode for the Prius at around $4K. If this would happen the Prius would become a true plug-in hybrid and that would be cool. I also think a lot of people would then look to buy a used Prius and upgrade the batteries. That all said it's justa pipe-dream at the moment.

Not sure a similar thing can be done for the Honda as the IMA system uses weaker electric motors.

For me the closer to EV technology in the Prius was the reason I decided to buy it instead of the Honda