Slinky knit (like Citiknits original fabric, Chico's Travelers) are not poly fabrics. They are various grades of rayon spandex. I don't care for the Slinky brand (what I tried was too thin), but do like Travelers and some of Citiknits. Weights varied with the Citiknits - some are substantial, some are flimsy. Chico's Travelers are probably the ones I like the best.
I prefer SG's butter knit over the liquid knit. I like liquid knit, but only for "some" tops. It's just not substantial enough for me for pants or skirts. Personal opinion only.
If I had to choose just one, I'd go for the rayon/spandex knits.
I'm fussy about fabrics ... I prefer SG's butter knit over the liquid knit.
ETA: For pants ... I like SG's lustra knit.