I would base my decision on whether or not the data about both is essentially the same:
- If it is the same, except for attributes, things which can be entered as field content (attributes), keep in one table.
- If you need to actually track different types of data about them, then probably separate tables.
Keep in mind that a simple radio-button field can be used to differentiate Customer / Store, and that info can be used for reporting them separately. But,
If you ever want to report on them all together, it will be simpler to keep them in one table.