Well both have terrible customer service, but at least Sainsbury's doesn't use a foreign call centre.
Asda has a reputation for attracting the poorer working class types who wouldn't pay more for groceries even if they were better quality, so I doubt a conversion to Sainsbury's would work.
On the other side of the coin, Sainsbury's tends to attract the middle classes who can't afford or won't pay M&S prices, so Sainsbury's is used as a middle ground. Any willing to shift downmarket will already have done so to the likes of Lidl etc. They console themselves by saying that they are shopping continental as opposed to budget shopping
I wonder if they mean combining their purchasing functions, distribution etc to increase their buying power and achieve economies of scale, rather than the actual stores themselves?