ISPs can offer better speeds for different pricing, but they can't manipulate the content. Which means you can shop around for a better level of speed, but all the content is treated the same. With the ending of net neutrality, your ISP can manipulate the rate at which you download some sites, or not allow you to download them at all. To use your analogy with the power company, you may find the power provided is limited when they know you'll need it most and charge a premium to access it "fully".
If your ISP decides to take some retarded moral stance, you may not like that they are the ones deciding whether or not you can go to a sports gambling forum. Or, for the privilege to visit that forum, a premium may need to be paid for the gambling package.
Thank you - this response was very helpful!