The 360 does have a cooling fans. Don't tell me you've never heard them. It's like an airplane taking off.
But -as you noticed- the Xbox360 does have a relatively high failure rate. Although the newer and higher-end elite models supposedly run a lot cooler and have a lower failure rate.
The PS3 isn't entirely free from failure either, but it does have a significantly lower chance of dying on you. The slim PS3 isn't known to be weaker than the fat one. Neither was the slim PS2 for that matter.