The standard PS5 has access to 5GB, and the Pro 5.5GB. The 1GB of DDR3 free up 512MB of GDDR5. 

The PS4 has access to 5gb of GDDR 5 RAM not 4.5gb. Other than that not all RAM is equal, otherwise everyone would have DDR3 ram with a low clockspeed of frequency or whatever you call it. Same counts for hard discs and SD cards. The reading speed of an SD card can be faster, but it isn't garuanteed. In the end the answer to the Switch vs Xone, Wii U and PS4 is always the same. It isn't comparable with the PS4 Xone but it's stronger than the Wii U.

On a side note total memory of PS4 is 8.5 GB. 512 MB is used for standby downloads. PS4 Pro actually had 9.5 GB memory.

not sure if you have an irony detector, but my first reply was to you saying they will have some type of expansion for the switch. now unless you're in the board meetings of Nvidia or Nintendo and have access to some confidential plans, you were probably pulling it out of some hole.

so assuming we both were giving our opinion on what's more likely to happen in the future, let's say my opinion is backed by decades of videogame history of no successful modular console ever existing.

Nintendo invested $100m in DeNA initially for this OS. It has a capacitive, multitouch screen that will be not be used in games, meaning it's likely just for the OS. There's absolutely no way the Switch will have a simple OS.

Now that's an intersting post.

Would you mind linking to the article these are from? It's somewhat meaningless without context :p These graphs aren't particularly relevant to the discussion anyway (we don't know how much usable RAM the Switch has, the PS4, X1, and maybe Switch are all using different types of RAM, and frame-rate isn't the core reason for wanting more), but i'd be interested to see it regardless ^^

simple in terms of ram usage, could use even less than the wii u.

https://fossbytes.com/4gb-8gb-or-16gb-how-much-ram-do-you-need/

Obviously this is for PC. All other settings are the same, only RAM is changed.

Technically resolution could have an indirect correlation with RAM usage. When resolution is higher, textures are also more likely to have higher resolution, and textures have to be loaded to the GPU somehow. I don't have very deep knowledge of graphics, but you might have to load the textures to RAM first. Of course if it's possible to 'stream' textures to the GPU, that's not much of a problem, but that's the part I don't know about. Anyway, if it's a unified architecture, where both the CPU and the GPU use the same RAM (which I assume is the case with Switch), it's probably not even a relevant detail because the textures will be stored in RAM anyway.

Actually the extra seems to be 256 MB instead of 512 MB, and it's on a separate CPU. At least that's what Wikipedia's telling me.