I demo'd the Watea 84's and Legend 8K's at the end of the season (I wanted to try the iM 78 too, but they were unavailable) - see my review @ http://forums.epicski.com/showthread.php?p=895437
IMO the choice will depend on your technique, which one comes in the length that works for you best, and how you like a ski to feel (the not-to-helpful "it depends" answer - sorry). I found the Watea more of a carver (i.e., it works best while holding a controlled, edged turn), while the 8K preferred straightlining and swiveling/skidding a bit more.
Of course, here in Colorado, like UT, fatter is probably better (unless you want to use these as a harpack ski), so that would give a nod to the Watea's (they performed great in a foot of fresh snow - the 8K's worked almost as well but were definitely less floaty).
OTOH the Wateas are fairly forgiving and respond better to subtle input, even for a 130lbs lightweight like me. So a hardcharger probably wouldn't like them (or the 8K's), which seems to be the consensus on this website. The iM78's or even the 82's are supposedly beefier and welcome more powerful input (again based on what I've read on this website).
The conclusion - the Watea's fit my technique better than the 8K's (and better than a few other skis that I tried that day, along with possibly many others from my skiing memory bank). I loved them and now own a pair of 167's.
Happy shopping and then waiting for the next ski season!
I have tried the Mythic Rider and I, contrary to most reviews I have read, felt it was extremely stiff and did not do well at slower speeds. My conclusion from that is that I am NOT a hard charger. FWIW I skiied with Peter Keelty and he said that I am a "strong" which is mostly traditional technique ranking 8/9 on a scale of 10. I have also tried the Legend 4800 which was great until you got some speed and then I wasn't comfortable with it. So, It seems to me that for an everyday ski at Solitude and Snowbird (unless deep powder day) the ideal would be in order of preference: the Watea, Legend 8k and then the Head. Does this seem logical?