A:Answer Hello Ginny - this is Nancy at GE and I am happy to help you.
The main two differences between the two double wall ovens is that the PT9550SFSS has two convection ovens, whereas only the upper oven is convection in the PT7550SFSS. Also, the PT9550SFSS has the Notification Lighting, which is a status LED light bar tucked away between the top of the oven door and the underside of the control panel and serves two distinct purposes.
The first is a pre-heat status update. While the oven pre-heats to the selected temperature the entire LED light bar with pulse will let you know at a glance that the oven is in pre-heat mode. Once the temperature selected is reached, the oven will beep and the light bar will glow solid for the remainder of the cooking cycle.
The second function of Notification Lighting is as a status update to the timer. When the timer is set, the LED light bar will collapse to the left and slowly build across the top of the oven as the timer counts down. This allows you to quickly check how far you are in the cooking cycle from a glance across the room. The Notification Lighting functionality can be deactivated if desired.
I hope this helps! Thank you for contacting GE!