They are a lot smarter than Sainsburys. I lived in Belfast when Sainsbury opened their first NI store. Their planning obviously just went Belfast=Capital=London so they stocked exactly the same high-end products they would in Earl's court, so 18 brands of extra-virgin olive oil but no bacon.
Tesco's system is smarter. There are 4 Tesco in Cambridge in different parts of town and all have a different type of stock to fit the local market even in such a small town.
Tesco is expert at tailoring their ranges to exactly the sorts of local customers. Most big chains try to standardise ranges across the entire company in search of non-existent efficiencies.
Tesco realises that what a shopper in the poor area of Belfast wants is quite different to a middle-class Glasgwegian, and it profits accordingly.
Tesco's system is smarter. There are 4 Tesco in Cambridge in different parts of town and all have a different type of stock to fit the local market even in such a small town.