No scientific proof at all but it feels like washing powder does a much better job at removing stains than washing liquid.
It also seems more and more difficult to find washing powder in store as manufacturers are moving to liquid and even more a rip off - pods. Don’t get me started on these money spinners.
What is your experience and what works best?
It depends on the brands. Some wash better, some leave better scent, some have built in softner, etc. So maybe the product class alone is not enough to judge.