I would recommend the RRS SC based solely on its suspension, the additional power is just a bonus. It comes standard with the hydraulic anti-sway bars I mentioned above, and also come standard with Terrain Response II - which most V6's do not. In fact, I would suggest a 2014 or 2015 SC over a 2016 V6 HSE, because the mechanics of the SC have remained virtually unchanged. The advantages of buying a 2016 are: (1) the potential for a longer effective warranty and (2) the updated infotainment system (which, personally, I could care less about, but some other folks might feel differently).
If you're not going to spring for the V8, I'd suggest the diesel. It has great torque delivery, which makes it a pleasure to drive day-to-day, and get's killer highway mileage.