Hi Jeff
Firstly I am pretty sure the Hillybillys I have are the older compound, they recently changed the spec so any comparison may not be so valid anymore.
For various reasons I haven't put as much time in the worst weather on the Michelins as I have on the Hillybillys, but all I can really say is I loved the Hillybillys for the conditions I was riding in last winter, which round me is pretty much ankle deep mud or washed out clay, I found they gripped really well whilst being predictable (which is what I want most out of a winter tyre), were not that draggy, and I didnt once have a puncture. I am not riding any sort of terrain that has exposed rocks with slippery faces, so cant comment on that, but they worked well on roots. If I was to try and sum up my experience with them is that they are a tire that just keeps going in the worst the weather can throw at you, dont get clogged up, and allow you to get on with riding.
The Michelins have been great so far, I have ridden them a fair bit in the wet and no complaints, and again I would say a tyre you can trust, they plough through the mud too, but IMO the best thing about them is the side knobs, which for me have taken my confidence in what a tyre can do in a corner to a new level.