I too use sugar and cream. I use cotton because I want them to be easy care. I don't want to have to worry about them felting while I'm scrubbing in hot soapy water, or in the wash. If I'm going to actually use my dish cloths, I need to make sure that all that needs doing is getting tossed in the laundry bin and washed with everything else. I do find that the way I've been knitting them up is a little too loose for true scrubbieness, but I got some tulle I want to try knitting with strips of, and I make t-shirt scrubbies that are the most scrubbie thing in the the world, and yet not abrasive, i'd use it on the finest china. Its brilliant. I just cut strips of non-stretchy cotton t-shirts, and knit em up. Speaking of dish cloths, I should go make some more.
In terms of pattern, I do all sorts of things, I'll make rows, columns, and seed stitch, I once tried a sort of waffle weave, and simple stockinette. Honestly, I like the stockinette because its fastest, and there are no performance differences between them in my opinion. I would like to try making some cabled ones (but need a cable needle), and some diagonally made ones (need to learn knit together and yarn over lol)