I've always used my PS3 in horizontal mode, and when I've tested the temps in MultiMan, vertical mode had the exact same temps for CPU/GPU.
My question is that, besides the CPU/GPU temp can there be any difference which can't be measured this way, but may be important?
Also, which way does the PS3 has better airflow? My main concern is that I don't want to get YLOD as long as possible, so if someone can help which way is better (if there's ANY difference) it'd be nice
Fat models are only one who are capable making PS3 in vertical position without extra support (like stand in slim models)
but yeah, if its case to case scenearion, when in horizontal position the console is very secured since it has its all weight position 4 feet, rather than 2 feet. Also In vertical position, you are blocking the extra vent holes there (which is a intake vent holes).