My experience with Hannaford is that my total tabs there average about the same as my Market Basket receipts. Perusing the Stop & Shop flyer, on the other hand, is like reading the Sunday comics.
Yes, some of their sale items are well-priced but their regular prices have always run high. They seem to have retired their TV ads from a few years ago which featured their reusable green tote bags carried by stereotypical soccer mom types averring their commitment to economizing and declaring that Stop & Shop "works for me".
The merger exploration is at an early stage. I would think that if it happens, Hannaford prices will rise rather than Stop & Shop's decreasing.