There are some novelty yarns that are acrylic, that I like, including the one I think you're talking about. But the average, el-cheapo "grandmother's afghan" acrylic just isn't my thing. I've made a few things with it, including an afghan (couldn't afford anything else--at least the colors are nice and bright), and a few kid's sweaters (it does wash well). But I've just seen so many cheesy things made from cheap acrylic yarn, that I associate it with cheesy patterns. You never see store-bought things made with that yarn. Plus, I tend to avoid synthetic fibers. For environmental reasons, and the fact that they don't breath as well.
Also, I just prefer wool, in general. It's much warmer than acrylic, and warm is what you want, when making a hat, or sweater, etc. Also, you can do a felted join with it, which is stronger and saves time. Also, it's natural and environmentally friendly. Plus, they now have all sorts of really soft merino blends, as well as machine washable wools. I know they're more expensive, but I tend to knit smaller projects anyway, so I never have to pay much, and I just love them, they're such a pleasure to work with!