I think a couple of replies are missing one aspect to your question. If you have more RAM and you use it, you'll probably have more processes to drain the battery. I noticed this when my desktop went from 8GB to 16GB under Unity and extra Google Chrome/Vivaldi/Firefox tabs.

On the other hand, it encouraged me to buy a faster and more energy efficient graphics card, run i3wm, and buy an SSD. That fixed the problem.

So a laptop with 32GB RAM might mean you'll push it harder, but I guess it also opens up the opportunity to run VMs, etc. Regardless, highly-specced device is cheap, Apple or otherwise.

At the moment, I think my favoured approach is an ultrabook + desktop system. Laptops will never be desktop replacements so long as you can pack more punch per dollar into a desktop. As usual, it's horses for courses. I think ultrabooks are best used as devices of focus and for mobility. Putting the kitchen sink into them doesn't make a whole lot of sense, usually.

No appreciable different at all, with a 35W processor RAM power consumption just isn't an issue.

I think power consumption by RAM is more affected by the number of sticks rather than their capacity. As long as they're only 2 slots (most laptops are except ultra-high-end machines), the power difference between 16GB and 32GB should be negligible.