The assumption here is that the MacBook is better because of soldering components rather than because Apple simply made a better chip and has a better OS than Windows.
Is there a reason to believe that if Apple didn’t solder memory on, it would make the performance/battery worse, as opposed to making the device slightly heavier/bigger?
Apple Silicon is a slightly customized ARM processor soldered onto a main board. That's not the reason for it's better performance.
Microsofts support for these is still kinda bad ime, which is easily the biggest impact on their battery longevity.
Furthermore, Most super intrusive and performance hindering spyware aka antivirus is only deployed on windows, hence it gets double-punched by having subpar processor support and wastage in the processes running in corporate environments. The latter being the biggest performance impact.
These are however all software, not hardware bound issues
Yes, if they did not solder on the memory it would use more power. The longer the lines are to your DRAM, the more impedance there is and you need higher drive power on your memory controller. LPDDR has been soldered forever as far as I know, though with the introduction of CAMM (compression attached memory modules), this has changed. I don’t know but I would bet money CAMM is still higher power for less bandwidth than DRAM packaged on the SoC base die or however apples does it.
> The assumption here is that the MacBook is better because of soldering components rather than because Apple simply made a better chip and has a better OS than Windows.
That's your assumption - my point is that I don't care as long as it's actually good. The only part I really care about is the battery because it has a limited number of cycles that is shorter than the lifetime of the rest of the components.