https://www.notebookcheck.net/No-the-PS5-won-t-offer-anywhere-near-the-graphics-performance-of-Xbox-Series-X-Navi-benchmarks-prove-it.458625.0.html

I really don't think that the slower SSD is going to be a big issue for XSX. We're still looking at I believe a 40x I/O speed increase compared to the archaic 5400 RPM laptop hard drive that was used in base Xbox One, that is a massive increase. We also have to remember that MS claims to have worked a bit of software wizardry to partially offset the disadvantage of their slower SSD, with their Velocity Architecture which is designed to optimize texture streaming and reduce the CPU overhead of decompressing textures. Those claims could be secret sauce bunk, but if they turn out to be true it will offset alot of the disadvantage of the slower SSD. Xbox Series X also has access to DirectX12 Ultimate features, such as Direct Storage, which is designed to further optimize texture streaming.

We also have to remember that 3rd party multiplat devs always try to make things simple for themselves and optimize for the lowest common denominator, then scale up from there, the vast majority of them are not going to do extra work to take advantage of PS5's faster SSD when it comes to things like faster flight or having no elevator loading screens like have been talked about as an advantage of PS5's SSD, so the PS5's SSD advantage will mostly show itself with faster initial load times and fast travel times and maybe a bit less noticeable level of detail pop-in on 3rd party multiplat games. It'll mainly be the 1st/2nd party devs who are able to take full advantage of PS5's faster SSD.

We also have to remember that there are 2 very good reasons why MS went with a slower SSD:

1. Price. A custom SSD like the one Sony used is going to be alot more expensive than the basically off the shelf SSD XSX is using.
2. Expandable storage. MS wanted users to be able to easily expand their storage, so they went with an internal SSD that was roughly the same speed as the SSD cartridges you will be able to buy and plug into the port on the back of the system. Sony on the other hand, while claiming to have expandable storage, won't be able to sell SSD's as fast as their expensive custom internal SSD, so you'll have to expand it's storage with a slower off the shelf SSD, which will handicap the performance of any games that are designed to take full advantage of the fast internal SSD if you install them on your 2nd SSD.

I really don't think that the slower SSD is going to be a big issue for XSX. We're still looking at I believe a 40x I/O speed increase compared to the archaic 5400 RPM laptop hard drive that was used in base Xbox One, that is a massive increase. We also have to remember that MS claims to have worked a bit of software wizardry to partially offset the disadvantage of their slower SSD, with their Velocity Architecture which is designed to optimize texture streaming and reduce the CPU overhead of decompressing textures. Those claims could be secret sauce bunk, but if they turn out to be true it will offset alot of the disadvantage of the slower SSD. Xbox Series X also has access to DirectX12 Ultimate features, such as Direct Storage, which is designed to further optimize texture streaming.

We also have to remember that 3rd party multiplat devs always try to make things simple for themselves and optimize for the lowest common denominator, then scale up from there, the vast majority of them are not going to do extra work to take advantage of PS5's faster SSD when it comes to things like faster flight or having no elevator loading screens like have been talked about as an advantage of PS5's SSD, so the PS5's SSD advantage will mostly show itself with faster initial load times and fast travel times and maybe a bit less noticeable level of detail pop-in on 3rd party multiplat games. It'll mainly be the 1st/2nd party devs who are able to take full advantage of PS5's faster SSD.

We also have to remember that there are 2 very good reasons why MS went with a slower SSD:

1. Price. A custom SSD like the one Sony used is going to be alot more expensive than the basically off the shelf SSD XSX is using.
2. Expandable storage. MS wanted users to be able to easily expand their storage, so they went with an internal SSD that was roughly the same speed as the SSD cartridges you will be able to buy and plug into the port on the back of the system. Sony on the other hand, while claiming to have expandable storage, won't be able to sell SSD's as fast as their expensive custom internal SSD, so you'll have to expand it's storage with a slower off the shelf SSD, which will handicap the performance of any games that are designed to take full advantage of the fast internal SSD if you install them on your 2nd SSD.

They did detail what Velocity Architecture and DirectX12 Ultimate features will do for Series X, at least somewhat:

Yes, but MS is going to sell SSD cartridges that match the speed of the internal drive soon after the launch of the system, meaning that you will be able to install Series X games on your 2nd SSD with no disadvantages. Sony is not going to be selling SSD's that match the speed of their internal SSD, and we won't see off the shelf SSD's that have speeds over 7 GB/s for at least several more years, at least not ones that are affordable. Which basically means that you are limited to the the 825 GB internal SSD for the first several years of the generation, which will be more like 750 GB accessible by the player thanks to space taken up by the OS. You can expand PS5 storage with a slower off the shelf SSD, but you will basically only be able to install PS4 BC games to it, as PS5 games will be optimized to take full advantage of the faster internal drive, and therefore PS5 games would run like dog crap if you tried to play them from a slower off the shelf SSD. 

Wait, are you telling me that PS5 doesn't have 2nd, empty internal SSD slot? I could have swore I read somewhere that it does. If it only has the one slot, that is even worse than I thought. It would mean that you will have to replace the 825 GB one it comes with with something larger in order to get more storage, which will be even more expensive. On XSX, you should be able to buy a 1 TB SSD cartridge to pop in the expansion slot on the back for about $150 (the price of a 1 TB NVMe SSD currently), doubling your maximum storage from 1 TB to 2 TB. On PS5 you would have to wait until SSD's as fast as the internal one are available off the shelf, and then buy a 2 TB one, which would likely cost $300+, if not $400+. 

What Otter says is true. What you believe is what you want to believe. Like you only believe that SSD is the key to nextgen for the simple reason that its the only thing that PS5 has thats faster then XBSX so clearly your going to cling to it like its some holy grail. However yes SSD will be great for Nextgen but it wont be only a benefit for just Sony to enjoy or mean the PS5 will have games that wont be possible on PC/XBSX.

And here I thought that PS5`s Audio Tempest was a more powerful solution than on XSX.

quite sure everything depends on your hifi-set

At minute 21 of the road to PS5 video, he talks about the expandability of the internal storage. Indeed there seems to be an internal bay (20:55 of the video), but it only supports certain M.2 SSDs.

This article is also interesting:

https://www.forbes.com/sites/kevinmurnane/2020/03/25/the-xbox-series-x-has-a-good-solution-when-its-ssd-gets-full-the-ps5-doesnt/

I'll quote the most relevant part:

"Sony took a different approach. Instead of designing for a custom external SSD, Sony opted to include an SSD-ready internal drive bay. There are two problems with this. The first is there currently are no SSDs to go in the bay. SSDs have to work with the PS5’s advanced technology and those SSDs don’t exist yet. Mark Cerny, the PS5s lead system architect, cautioned that once these SSDs are built, they have to be vetted by Sony to make sure they fit in the bay that’s provided and work with the PS5’s custom tech. That’s going to take time. Cerny expressed hope this problem will be solved before the PS5 launches, but he counseled patience because it might not be."

It's just that your original post was kind of wrong because Sony won't be selling SSDs, and also because it will be possible to purchase an additional M.2 SSD even though it will be limited to certain vendors and will happen after launch (time 23:30 of the road to PS5 video). Otherwise your conclusion matches the article and makes perfect sense so it shouldn't have been bashed, just corrected.