What?Your forgetting the single most important number here, memory Bandwidth.
32GB at the same bandwidth as the 16GB, gets you almost nothing.
My favorite way to think about these things is actually memory bandwidth / Per Frame.
lets take the PS5 as an example.
Mem bw = 448 GB/s,
At 60fps, that means a single frame can access a total of 7.466, GB of data.
Thats plenty of textures, models, render targets etc.
This also means that if you have a total of 16Gb ram, your NEVER going to access your entire ram in a the
process of rendering a single frame.
now a 30fps game, can access pretty close to the entire 16GB in the process of rendering a frame,
but even @ 30fps, using a 32GM ram over half would be wasted.
Now lets think about what a fast SSD gives us.
1. The ability to refresh our smaller pool of ram faster
2. The ability to cache more game state at any single time.
The faster refilling of actual RAM, is good because it simplifies the entire process.
HD or even slow SSD, are not quick enough to enable on demand paging systems for textures or other data structures.
The ability to cache more game state is a HUGE step forward - imho.
Richer, more living worlds, where game state only needs to be updated on a 1-10 fps basis, ie "the living world" that isn't immediately on screen.
will see a huge step forward this gen.
Now if your talking about 32GB @ 2 x 448GB/s, yeah sure the double the ram starts to make sense,
but now your no longer at price parity, even with no SSD. Thats 3090 prices.
Overall i think almost all developers, would opt for the 16GB + SSD option.
modern computing is well versed in the techniques for handling multi-level caching, and addressing across
memories of different BW and latency. But only once you get to decent SSD speeds, it all falls apart with a HD.
I think the MS approach of letting the SSD act as sort of a victim cache for the RAM is a very smart idea,
and does in theory give them access to 100+GB of total memory, which is all HW managed for best performance.
but it's a somewhat unique mechanism, and may not be fully exploited.
( I dunno if you can sue the PS5 the same way.. )
Memory bandwidth needs to scale with GPU performance and not necessarily memory size. Since we're not increasing GPU performance in my scenario then memory bandwidth doesn't really matter.
Having more RAM would most definitely help offset slower SSD performance with intelligent loading/caching techniques.