Getting ready to do a Mannington engineered hardwood install... will be "floating" on an at-grade concrete slab. I have seen two types of "premium" underlayments that both have the requisite vapor barrier for moisture protection. Lowes has one that has a felt-like or fibrous mat layer, while Home Depot has Roberts 3 in 1 foam underlayment. Both are similar price ($50-60 US), have the vapor barrier, and are good for 100 sqft. The foam rolls are about 1/3 the size of the felt type since the material is thinner. Home depot also had some much cheaper foamlike products that I have not researched or considered.
Is there an advantage to one type over the other in this type of install? Mannington seems to sell their own version that looks more like the Roberts foam type as far as I can tell from online info.