Well AP, the GS is one sweet ride.
I'll get the negatives out of the way first:
1) Back seat is okay for room but actually less than my Sonata. Perhaps not a negative per se - as it is quite comfortable for two adults - just not spaciously so. More like it is not a strength.
2) Tiny trunk IS a negative. No way I could haul 4 adults AND 10 days worth of luggage for an east coast road trip as I quite easily did in my Sonata. Rear seats do not fold down so I can fuhggedaboud stuffing my bike in the back.
3) That predator grille still doesn't float my boat, but the 2013 version is positively tame as compared with the 2016 version.
The good stuff? Everything else.
The car presents VERY compelling blend of sport and luxury. Much more responsive and light on its feet than the LS. Still a comfortable smooth-riding car in normal mode, but twist dial to SPORT PLUS and things tighten up significantly.
While down on cylinders and power to the LS it feels quicker - which is mostly down to deceptive effortlessness with which its big brother gathers speed. And that V6 makes VERY pleasing sounds in the upper revs - which adds to the appealing dual personality of the vehicle.
The interior is absolutely stunning, IMO. While the LS is more old-school luxury, the GS interior is very techy and contemporary and I LOVE the super-wiiiide split-screen display. I love the fiddly mouse controller for inputs a good deal less. I expect I'd get used to it, but I found it a challenge to use while parked and not at all a good idea to use while driving.
Very tough call between the two as they are very different. The GS doesn't have that velvet bank vault feel of the LS and isn't library-quiet inside. Its seats are very good indeed - but the LS thrones are excellent. Comparably priced, I'd be looking at a 2011 LS and a 2013 GS - so definitely newer and likely less mileage if I go with the latter.
Then there's the fact that when I think about it, the Genesis arguably splits the difference between the two. So decisions? No, not yet.