I like IconDaemons approach, but there are many reasons you would not want to do that. Therefore I am going to give an alternative answer.
In short: I would recommend the MBA over the MBP for several reasons:
- no/minimal dust build-up
- no moving parts, less risk of hardware failure
- quiet, no fan sound at all
- minimal performance difference
The only real technical difference between the two machines is active cooling with a fan on the MBP compared to the MBA. This difference implies the major differences mentioned above, which are all positive, except for the performance difference. Yet, if you compare the two MacBooks, this difference is very small and only occurs after long and heavy workloads:
Only after ~10 minutes under full load the MBA experiences thermal throttling. In my opinion, most users even considering such a laptop do not need the higher performance after long workloads.
Considering the battery on the MBA already lasts more than a work-day (and it actually lasts this long, not only in tests), I'd argue you will rarely need the longer battery life on the MBP.
Now lets get to your questions:
Is it true that the Air without fans would be more bed-friendly than the Pro with fans?
In my opinion: Yes, due to the multiple reasons mentioned above.
If it is true, would disabling the Pro fans while in bed make it essentially function and relatively painlessly throttle like the Air?
Looking past the technical difficulties and the fact that that's not recommended, the answer would most likely be yes.
- However, what do you gain in doing so? This would basically make the MBP a more expensive MBA, yet still with fan intakes allowing dust to get inside.
Note: Someone using a laptop in bed is most likely not going to edit videos in FPC X, bounce huge Audio composition in Logic Pro X, test large iOS projects/Apps in Xcode,... and therefore not really gain anything from the MBPs higher performance under sustained load.
I know that the MBP also has slightly better speakers, a slightly brighter display (what do you care in bed?), better mics, but in the end, I don't think these small things are that important.
Here is a list of videos/articles comparing the two machines: