I like the look of embossing folders, personally, but I do have a couple of the Impressabilities. I have to use cardstock shims with my Cuttlebug until I get a good impression. I haven't tried them yet with my Grand Calibur.
Yeah, since they're thin and it's just a plate, it's naturally not as deep or crisp an emboss as a folder that has both a positive and negative to create an impression.
However don't forget the plates can also be used as a stencil for inking, or as a mask for Glimmer Mist or other spray. You can do inking techniques with a folder but there's no way to use them as a mask