There is this article which states the best and worst supermarkets of 2018.
It's not a professional study and it's done on a small number of individuals.
Access Here


You can clearly see that:

Lidl has the worst design, queuing time, staff availability however offers the highest value for money (this doesn't mean products are of high quality, only more affordable)

M&S has the best design and quality of OWN LABEL products.

Waitrose offers the worst value for money (products are of high quality but they are not affordable by the wide public).

At the end of the day, it depends from shopper to shopper. I believe that the financial availability makes the most difference on where you go shopping. You either eat an affordable Tomato Sauce with Pasta Fusili from Lidl or have a nice Foie Gras from Waitrose.

Something I wish you discussed is Amazon Fresh. Most people never used it but it's a nice experience.