I had the same purchase dilemma as you but "ultimately" (get it-LOL) I chose the 2015 Genesis AWD Ultimate.
Why? Because the Genesis is now in its second generation and has been vastly upgraded on SO MANY different levels (hundreds) than the Equus, which is still in its first generation and has not had a complete platform AND technology upgrade like the new Genesis. (Let's face it, the current Equus is similar in so many ways to the first generation Genesis 4.6 Tau you now drive, only bigger with the appropriate upgrades.)
There are literally hundreds of reviews published since the first of the year that you can search for online that dissects this wonderful car and heralds how good this second generation transformation of the Genesis really is. In fact some auto writers are comparing the new Genesis as THE "seminal" model for the Korean automaker's turning point for Hyundai's induction into the true luxury car business akin to Toyota's introduction of the Lexus LS400 back in 1989 which finally brought the Japanese into a similar orbit as the German luxury brands. The car is simply that good and hard for anyone to say otherwise (except ignorant Hyundai naysayers still living in the past).
I drive new press cars for a living for almost every major luxury auto manufacturer out there (you name it, I've probably driven it) and at the end of the day when it's quitting time, I LOVE the ride and serenity going home in MY new Genesis
In the future when Hyundai updates the Equus to the second generation Equus, similar to the redo of the 2015 Genesis, I'm sure that will be an equally impressive if not spectacular car shocking the industry and the Equus to buy (myself included), but until then the 2015 Genesis is the value luxury car to buy TODAY and a fabulous value at that, before the competition catches on