We have drove the JL Sahara but no dealer local has a JL Rubicon as of yet. They all tell me they are on the way. We drove the JK Rubicon and did not like the ride but we didnt hit the interstate with it. Mostly backroads.IMO, go with the leather, and then get a seat cover if you want to change the surface contact feel for weather extremes.
I find the leather provides better support especially in the bolsters, and to me is more comfortable for longer trips. I have summer light covers because the F’in black is a heat magnet (though not as bad as the bacon-sizzlin’ armrest IMO), but if you go with the light tan seats that will improve the sun/heat issue a bit... but... likely still a bit sticky when humid. Of course in winter when heated both are fine, and if it’s cold enough to matter, you likely have heavy enough pants/jacket to not notice that much.
I haven’t tried the new Rubi seats yet, still waiting on a test drive from my two prefered dealers, but the new cloth Saharas were ‘meh’ to me, and considering the positive reviews vs the JK seats I think the leather will still be the choice for me.