This is the way I look at it. If you could rate both platforms by offroad ability, the JKUR would probably be like a 9/10 and the GC would probably be an 8/10 (I realize my rating system is probably flawed, but you get the idea). The thing for you to do should be to take a good look at what your typical driving looks like, and whether or not it's of value to you to have that extra 10% capability. If you use your vehicle on-road or off road in milder situations, then the GC would probably be a good fit for you. If you're planning on tackling the Rubicon or similar, then take the JK.
There's other things to consider as well. The GC has a little more payload capacity than the JK (important for overland), but the JK has removable top and doors, as well as killer aftermarket support. JK probably has better resale value. All depends on where your priorities are, I guess.
Also, I don't know if you have it on yours, but the GC has those air-conditioned seats available that are just flat-out amazing (not to mention the lumbar support, as you said previously).
My dad has a '14 GC (just replaced his '12 GC), and I have a '13 JK. I drove both before I bought mine, but I obviously decided that the extra capability was more important to me than the comfort and other advantages of the GC.
Just be honest with yourself about your driving habits and plans for the platform. You can do a surprising amount of stuff with a trail-rated rig from Jeep. See the recent post on ExPo about the Patriot project.