I would suggest vacuming the vents if you dont already do that for dust.
Or take the case apart and clean the accumulated dust off the fan and other areas. it should not be noisy as a BD player, or even for games, though some games are more taxing on it than others and the fan will go to max. Some people say the thermal paste on the cpu is no good and should be redone on the fat models.
I think the slim are better for cooling somehow.
The super slim are terribly noisy, avoid completely if a disc is needed. They are ok apart from that. Its just disc noise.
That a great way to short the whole system out. Unless you ground the vacuum. So there little chance or shorting or frying your console computer laptop. Also remember to ground your self before touching any of parts of the unit.
Well about the thermal paste. Good point.
Now newer vs Fatter Models. Well Older PS3 had both xbox 2 and Xbox 3 chips on it.
There could also be smaller cpu & Graphics chip over time to cut cost and heat. Which could help in cooling.
Now smaller Unit like the PS3 slim type consoles. It could dissipate heat better vs the older models. Just because it can draw in cool air better to keep the unit cool. Just due to the smaller size.