I thought it was the opposite, I could be wrong, but Ive had both a phat and a slim, and my phat failed on me twice and my slims still running strong (although of course its in a sperate area of my phat, its with my wii so thats probably something.)
I know Im not an accurate representitive of failure rate as my wii has also broken twice, but I still thought that was how the PS2 failure was, I could bewrong I guess...