I grasp the difference in the size of the hard drive. However, I am not sure if there are any other differences between the Pro and the Plus regarding software, hardware, firmware. etc., While looking for a used Roamio with lifetime service I came upon the following ad on eBay which referred to an upgraded Plus...from a 1 TB to a 3 TB hard drive, a "Pro." TiVo Roamio Plus, LIFETIME SERVICE, HDD Upgraded to 3 TB, Slide Pro remote. 851342000193 | eBay Any advice, suggestions etc., would be greatly appreciated.