This is truly the ultimate question. I had a hard time deciding , but in the end, I decided to buy 32GB RAM, and configure up to a 2TB SSD for a 16 inch MacBook Pro M1 Max. One reason is that I currently have the 2019 16 inch Intel MacBook with 32GB of RAM and a 2TB HD. I edit video, do some color grading and color correction for video and a lot of photo editing in Adobe Lr, Adobe Photoshop and Capture One. My use case, requires mostly CPU, and GPU instances. In video, I use Davinci Resolve and sometimes FCP or Adobe Premiere. These applications rely a lot on CPU and GPU, so that's why I went for the most CPU and GPU you I could get. Although these applications can take up a lot of RAM, I have rarely needed more than 32GB of RAM. I would often run into bottle necks in CPU and GPU before I would ever run into issues with RAM.
With my photography work, its a bit of the same thing for my use case. I don't do heavy design work, so most of my photography work is heavy color correction and editing. And 32GB of RAM in my past experience has always been more than sufficient even with heavy Photoshop workflows. My wife is a print designer, and utilizes only 16GB of RAM, and she often hits her max in RAM, but not by that much and not often, so 32GB would be game changing for her.
I opted the funds I would have spent upgrading to 64, into storage space. Because I tend to run out of storage more often. I looked at my usage on my existing 2TB storage and it looks like I'm always close to about 1TB utilized, and I don't like to have a 3/4 full storage drive, so 2TB has become a sweet spot for me, where I have enough room to play, edit internally if I need to and don't feel like I'll run out anytime soon.
I also will note that I see massive performance gains, with this new unified RAM architecture. I also own a Mac mini M1, and have seen it perform in ways that are comparable to my 2019 MacBook Pro with 32GB of RAM, so there is definitely effieciancies I've seen. I almost feel like the RAM equivalencies are slightly different in the new M1 architecture. For example, a 16GB RAM M1 system "feels" more like a 32GB Intel system to me, as does a 8GB M1 system (which is what I have in the Mac mini) felt and performed similarly to a Intel based 16GB system. This is just based on tests utilizing my stack of applications above.
So with all that said, 32GB of RAM should be more than enough for most applications, and I would segment 64GB of RAM as a need for people utilizing high performance computing tasks, designed to utilize the maximum output of a system, which could include high performance computational "number crunching" (scientific computing), visual FX and gaming development, and heavy and I mean heavy motion graphics work. One other use case I might include is music synthesis and audio. Many of those applications require good amounts of RAM as it loads a lot of audio samples into RAM Cache for virtual instruments in music and sound design applications. If you load up a ton of tracks, that all loads up into memory, while the audio plugins utilize processors. So if you have heavy track counts with a lot of virtual instruments than 64GB might also be a justification.
The rest of the bunch wanting 64GB of RAM are folks that want it and can afford it, and that's perfectly good as well. After all, if you compare how much it would have cost you to upgrade to 64GB of RAM in an intel machine, you will quickly see that the system last year was more expensive. So the value in these new M1 systems are quite compelling when you do the math.
So that's my 2-cents on the use cases and the comparison/justifications of 32GB vs 64GB
