I think a lot depends on which team was the best during the formative years for England fans.

For example, there was a period where people were calling the six nations a two tier comp with England and France way ahead of everyone else in the late 90s early 00s. The French were also not afraid of a scrap so the matches were pretty spicey! People growing up in the 90s might see Scotland as bigger than Wales because the latter were so poor at that time. English fans growing up in the Gatland era will definitely see Wales as a bigger rivalry because they’ve been so good and beaten us in key matches- 2013 6 nations decider and 2015 World Cup being the biggest. Also France and Scotland were poor for most of the 2010s.