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?
Liquid is supposed to be concentrated, if you use too much and don’t rinse enough you won’t really remove smells/bacteria. As others mention, it is best to read manuals and instructions. If you don’t use enough your clothes will smell like the worst thing in the wash.
I hardly see powder for sale in any shops where I live, so liquid gets the convenience points.
When I do see powder, I buy it because it is useful for setting the delayed start on my washer. I used to do pods, but they are awful, especially the pods filled with liquid. The water is so hard where I live, maybe that had something to do with it.