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?
The comments here are interesting. There’s a very important detail you left out, and everyone is just assuming in their responses.
OP, what are you trying to wash? Laundry, dishes (in a dishwasher, or by hand), or something else entirely?