Here are some difference between iRobot Roomba 530 and 780.

Roomba 530 VS. 780
images from manufacturer

* Advanced Cleaning Head
The 780 features the Advanced Cleaning Head that improves the ability of picking up dirt, pet hair, and more.

* AeroVac Technology and Brush:
The 780 includes the AeroVac and improved brush system, these 2 things alleviate hair wrapping around the brushes, and it is
easier to remove the hair than the 530.

* Virtual Wall / Virtual Wall Lighthouses:
The 780 comes with 2 virtual wall lighthouses, while the Roomba 530 comes with 2 Virtual Walls.

* Control Panel:
The 780 features Touchpad Control while the 530 uses Buttons.

* Full Bin Indicator:
The 780 has a full bin indicator to tell you when to empty bin while the 530 does not.

* Debris Sensing
The 780 features Dirt Detect Series 2 that uses both acoustic and optical sensors to locate dirty spots, while the 530
features Dirt Detect that uses only acoustic sensors.

* Persistent Pass Cleaning
The 780 features the Persistent Pass Cleaning pattern to clean areas where it senses with more dirt.

* Bin Type:
The 780 includes the AeroVac Series 2 Bin which uses a powerful vacuum to pull debris and hair off brushes into the bin. And
it holds more than standard bin that the 530 uses.

* Filter Type:
The 530 use standard filter while the 780 includes the Dual HEPA Air Filters that eject cleaner air.

* Control Tool
The 780 comes with a remote control while the 530 doesn’t, the remote control allows you to control the Roomba without touching it.

* Extended-Life Power Management
The 780 includes the Extended-Life Power Management that improves battery life.

* Recharge Time
The 780 recharges faster the 530.

* iAdapt Responsive Cleaning Technology
The 780 features the iAdapt Responsive Cleaning Technology that helps thoroughly clean the floors, while the 530 has no.

* On-board Scheduling
The 530 has NO on-board scheduling while the 780 has this feature to allow you to preset the cleaning time.

* Extra Brush Cleaning Kits
The 780 has 2 Brush Cleaning Tools while the 530 comes with only one.

* Extra Brush Set
The 780 comes with 1 extra brush set including 1 extra bristle brush, 1 flexible brush, and 1 side Brush, whereas the 530 has none.

Similarities:
adjust between different types of floors such as from carpet to wood floors automatically;
return to home base to dock and recharge automatically;

Do you know other difference between Roomba 780 and 530, please share below, thank you.