My longies (actually I have 3 with Wool-ease!) are crocheted my Mom and Grandma with the dandelion dreamer pattern and they work great. I have some knit longies also and I prefer the crochet. The crochet is a bit thicker and holds pee better. The knit is more stretchy, which is nice, but it gets damp on the outside faster.
Crocheted longies are absolutely great, even in acrylic.