As I understand, the main difference is in the operating system. The D9 is faster and has some nice features the D8 doesn't have. For example, if you are in a vehicle module reading codes or viewing data, etc, you can touch the home icon at the top of the screen and instead of exiting directly to home screen like the D8, the D9 will bring up a menu, so you can switch to OBD2 generic or look at saved files or whatever and your current session is saved. I'm not aware of any differences in the actual capabilities, I have the Triton D8 (basically an Apollo with a lab scope) and the Apollo D9 and they both run the latest software updates.

James Kuhns
Owner/Technician
Auto Tech Solutions
Chatham, New York, USA