Here is some difference between iRobot Roomba 595 and 630:

Roomba 595 VS. 630
images from manufacturer

On-board Scheduling:
The 595 has on-board scheduling which makes it can be scheduled to automatically vacuum up to 7 times a week, even while you are not at home. Whereas the 630 doesn’t have the scheduling option.

Virtual Wall:
The 630 has only 1 virtual wall whereas 595 has 2.
The virtual wall keeps the robotic vacuum cleaner vacuuming within a specific area.

Accessories:
The 595 comes with extra side brushes, beater brushes, and bristle brushes, while the 630 doesn’t.

Please share your knowledge if you know other difference between them, thanks.