MAC Touch My Body is a very warm-toned, light-medium copper with a sparkle finish. It is a limited edition highlighter that retails for $39.50 and contains 0.51 oz.
MAC Mariah Carey Touch My Body Loose Powder ($39.50 for 0.51 oz.) is a medium-dark, rosy copper with flecks of lighter and darker copper sparkle. It was sheer, almost translucent, but it was surprisingly buildable--I applied it to my cheeks and expected more of a highlighting effect, but it actually yielded color and coverage. I thought the color was nearly identical to My Mimi but applied a lot better as it was more even.
When applied with the included pouf, it had sheerer, more all-over coverage, while applied with a tapered highlighting brush, it gave subtle color and moderate luminosity. As a cheek highlighter, it lasted for just over eight hours before fading. As this product is not yet released, there was not much on it with respect to concrete claims, so the rating is based on what most loose, highlighting powders are designed to do (as well as what I remember MAC's Iridescent/Loose Powder, which this one seems to be similar to--described as a highlighter with a "subtle glaze of colour"). I'll be checking for any additional/different claims when the product releases online.
FURTHER READING: Formula Overview, which is a detailed review of the range as a whole.
M·A·C Iridescent Powder/Loose is a finely milled mixture of mica and pigments that gives skin a subtle glaze of colour with intense pearl. It can be used on its own or mixed into other products like foundations or moisturizers to enhance their iridescent qualities. Designed to apply easily and uniformly, it blends beautifully and can be applied on bare skin or over foundation. Because it's so concentrated, it should be used sparingly at first.