I generally go with store own brands unless it is substantially worse than branded. Realistically, most of the matched products will have been produced in the same factories with minor recipe changes to keep the costs down in the own brands. For example there's a factory near here that makes bread for several different supermarkets and brands. Another example is an ice cream factory I worked in one summer, which made products for Safeways (as it was then), Del Monte, Sainsburys, Green & Blacks and other brands. While some recipes were very different for different products, matching items eg vanilla ice cream were the same recipe and ingredients but the branded one was double the price on the shelf.
A friend of mine worked in a cheese factory one summer, when they had been packing up some cheddar as an own brand basics range, she was shock when the conveyors belts were stopped, and the packaging was changed out for a premium M&S range and they started packing again. It was literally the exact same product but on the shelves was about 3 times the price in M&S!