Mobile CPU vs. Desktop CPU

This is an interesting subject because this was the very thing that moved me to start this site over 5 years ago. I was looking to buy a notebook and a company called AMS Tech came out with a model that was faster than the current crop of notebooks. I couldn't figure it out because Intel had not released a mobile CPU with that speed yet. When I asked AMS Tech, they said that it was a new CPU and that it was an indeed a "mobile" chip (and advertised it as such in their magazine ads). Well, to make a long story short, an engineer from Intel got involved and verified that AMS Tech was indeed using a desktop CPU and although AMS Tech never admitted fault, they got some backlash from one of their resellers (I think it was NECX). You can actually follow this whole thing by doing a Google Groups search as this whole ordeal was communicated through the comp.sys.laptops newsgroup.

I had thought the mobile vs. desktop issue would have gone away with the arrival of the Pentium IIs because the desktop CPUs came in those big VHS-tape looking packages. But as soon as Intel started doing desktop PIIs (and P3s and P4s) in the standard PGA/BGA packaging (the little square chip), the desktop CPU'ed notebook came back to life. So the question comes up again: Which is better, a mobile CPU or a desktop CPU in a notebook?

Maybe you're asking "So what?". Well... it basically comes down to heat, longevity and battery life. A mobile CPU runs cooler and more efficiently. This in turn gives you longer battery life and (in my opinion) more longevity.

But proponents of desktop CPUs will argue the following:

1. If you have your notebook plugged in all the time, than what do you need longer battery life for?
2. If a notebook has a good ventilation system, then the heat issue is irrelevant.
3. New desktop CPUs run at lower voltages than even the older mobile CPUs so it's okay to use them now.

1. Heat: Even though it can be argued that current desktop CPUs run at lower voltages than mobile CPUs did 3 years ago, that doesn't necessarily translate into less heat. Doesn't it seem like today's CPUs even put out MORE heat than they used to? 5 years ago, a desktop CPU didn't need a heat sink or cooling fan, have you seen what you need today in a desktop system? A heat sink AND a cooling fan (and the heat sink is HUGE). To me, this just doesn't make sense to have one of those things inside the confined spaces of a notebook. Also, you have to remember that the CPU is not the only source of heat in a notebook. You have these bigger and faster hard drives, DDR memory and the high memory/high speed video chips producing more heat than in the past. So wouldn't it make sense to have components that produce the lowest heat possible?
2. Longevity: Well, simply put: Heat kills. So over a period of time, if the average life of a notebook is 2 to 4 years, excessive heat will damage something. I asked desktop CPU'ed notebook owners to get back to me 2 or 3 years after they bought their notebook and let me know if their system is still running fine. I haven't heard from any of them. Yet I do see tons of true mobile notebooks still being sold on Ebay that are still working. A fellow programmer has a Gateway Solo 9100 (a mobile PII 233mhz) that is still running great and he's had it for almost 5 years.
3. Battery life: This needs not be argued, it's a fact that mobile CPUs give you better battery life than desktop CPUs. And what if there isn't an outlet around? All I know is I can get 3+ hours out of my notebook (WITHOUT power saving), can a desktop CPU notebook do that?
4. Portability: As far as I'm concerned, notebooks were meant to be PORTABLE computers. Have you seen the size of those desktop CPU'ed notebooks? I'm sure they do it for better ventilation and stuff but still, I'm getting older and I can't lug around those things on a daily basis. I prefer a thin and light notebook -- and I have yet to see one that uses a desktop CPU. When the Centrino CPU (aka Banias) comes out, it should demonstrate the importance of mobile CPU technology and how it affects the physical dimensions of a notebook.

And again... to all those desktop CPU notebook owners out there who probably disagree with all my opinions, let me know how your system is if you've had it for at least 2 or 3 years.