One other advantage of leather is usually less static buildup. I used to get shocked nearly every time I got out of my car with cloth seats in the dry Colorado environment, and that issue went away when I got leather seats in the next car.

As for the heat with the black seats, just make sure to get a good sun shade and use it if you park in direct sun. I have all my windows tinted and also use a sunshade whenever I park, and it's worked well enough to deal with the heat issue. The worst thing for me beyond the seats has been the metal gearshifter. If I let that sit in direct sunlight, I usually have to wait a few minutes before driving off.