In my experience, companies reducing the size (ie, shrink) is much more common than them reducing the quality (ie, skimp) of products - without also reducing the price. But that’s not the question.

My thinking is that people typically notice shrink much sooner, if not at the time of purchase decision-making then once they get it home, perhaps. In contrast, skimp is likely only noticed when one goes to use the product - disappointment at at time when they might not have any alternatives. So, I’d guess that, pound for pound, people would hate skimp more, because it’s more inconvenient and perhaps more salient.

I can’t recall any examples of skimp in what I’ve purchased. But my mum got a package of salad mix and the frizzy type of lettuce that should be about 15% volume was 66% if not 75% of it. She was irate lol.

(By the by, I agree that shrink vs skimp are useful descriptively, but the term shrinkflation is inclusive of skimping [ie, lower quality products])