Cloth may be warmer in winter but that's why heated seats appear on the options list.
That aside, you leave the roof down in direct sunlight and, be it leather or cloth, it ain't gonna be comfortable.
Also, if you're unfortunate enough to get bird poop (damn those seagulls), ice cream or kiddy puke on your cloth seats then good luck getting that out. Leather wipes don't just clean with a wipe they also revive and protect the leather. JMHO.