1. I am not saying that you get an HDD to run the games of from, I am saying you get a HDD as a backup drive. Copy games that you are done playing onto it fr whenever you may want to play them again so you can then move them back into your system drive. Which would be faster than redownloading or reinstalling from disk. Basically your game on the external HDD would work as if you have a disc copy of the game. 
2. I don't know about MS "proprietary" SSD,I was under the impression that its just a 2230 M.2 SSD. In an enclosure. Thy use it for some of their devices and its a form factor that's found in some laptops too. I could be mistaken though.
3. That's a lot of storage space you are packing. Well for me, knowing how I play games; I start a game, usually don't move way from it till I platinum it or I'm done with it and that's it. Never go back to play it again. Then I have a couple of resident games in my system. Usually Tekken and GT ( my idea of pciku and play games. 
   
   So for someone like me, just getting an external drive that I can use as a backup drive would be great for me.

3,0 USB support for external drive, which could even be a cheaper large SSD if you decide as well. But I wouldn`t hope for automatic management of what goes to SSD or stay HDD since that would be external. Still if it allows you to play a game on the SSD while copying another that is perfectly fine for me.

Because those drives are insufficient from a performance perspective to load next-gen games from.

Microsoft has taken a performance-guaranteed approach with it's propriety "memory cards". - But that will be more costly.

Sony however is not as propriety, but there isn't enough details to showcase how flexible it truly is or what it's costs are.

I actually like having all my games installed and updated... I have 20~ Terabytes worth of storage on the Xbox One X, 4 Terabytes on the Xbox 360... 50 Terabytes on my PC.

Shit could get expensive for me next gen if I spent $100 per Terabyte...

1. I am not saying that you get an HDD to run the games of from, I am saying you get a HDD as a backup drive. Copy games that you are done playing onto it fr whenever you may want to play them again so you can then move them back into your system drive. Which would be faster than redownloading or reinstalling from disk. Basically your game on the external HDD would work as if you have a disc copy of the game. 
2. I don't know about MS "proprietary" SSD,I was under the impression that its just a 2230 M.2 SSD. In an enclosure. Thy use it for some of their devices and its a form factor that's found in some laptops too. I could be mistaken though.
3. That's a lot of storage space you are packing. Well for me, knowing how I play games; I start a game, usually don't move way from it till I platinum it or I'm done with it and that's it. Never go back to play it again. Then I have a couple of resident games in my system. Usually Tekken and GT ( my idea of pciku and play games. 
   
   So for someone like me, just getting an external drive that I can use as a backup drive would be great for me.

1. I am not saying that you get an HDD to run the games of from, I am saying you get a HDD as a backup drive. Copy games that you are done playing onto it fr whenever you may want to play them again so you can then move them back into your system drive. Which would be faster than redownloading or reinstalling from disk. Basically your game on the external HDD would work as if you have a disc copy of the game. 
2. I don't know about MS "proprietary" SSD,I was under the impression that its just a 2230 M.2 SSD. In an enclosure. Thy use it for some of their devices and its a form factor that's found in some laptops too. I could be mistaken though.
3. That's a lot of storage space you are packing. Well for me, knowing how I play games; I start a game, usually don't move way from it till I platinum it or I'm done with it and that's it. Never go back to play it again. Then I have a couple of resident games in my system. Usually Tekken and GT ( my idea of pciku and play games. 
   
   So for someone like me, just getting an external drive that I can use as a backup drive would be great for me.

Even if it was just that it is proprietary (which doesn't mean we can't see non authorized 3rd party cards).

The enclosure ensures form factor and thermal dissipation, plus the inside have the bandwidth ensured.

While SNY's SSD tech may be somewhat more expensive than what MS is using, you'd think if a proprietary card was going to be in the same ballpark price wise, that SNY would have gone with that.

To me, SNY saw the price difference for creating something like MS has, and decided it was going to be way too expensive. Not just at launch either. For the effort SNY went to in creating some of the hardware, like the controller for the SSD, why they wouldn't go to the trouble of what MS did with a proprietary card says to me it's price that was the biggest problem.

That's not to say MS's card wouldn't be cheaper right off the bat based on it's tech, and maybe MS is willing to subsidize those cards to some degree. I also can't help but wonder if MS assumes most will just transfer over their existing external HDD's, or upgrade to a larger one based on the much cheaper market prices.

The cost over time also needs to be taken into account. A proprietary card only comes down in price a lot if MS keeps subsidizing it, or if they sell a boat load of consoles, while also convincing many to buy 1 card or more. Mass market gen 4 NVMe's will naturally drop in price much quicker, which also means lower prices or higher amounts of storage for the same old price as years go by.

Well the SSD for PS5 being twice the speed would probably mean it would cost more to manufacture than MS solution even with the heatsink and other stuff on the stick.

While SNY's SSD tech may be somewhat more expensive than what MS is using, you'd think if a proprietary card was going to be in the same ballpark price wise, that SNY would have gone with that.

To me, SNY saw the price difference for creating something like MS has, and decided it was going to be way too expensive. Not just at launch either. For the effort SNY went to in creating some of the hardware, like the controller for the SSD, why they wouldn't go to the trouble of what MS did with a proprietary card says to me it's price that was the biggest problem.

That's not to say MS's card wouldn't be cheaper right off the bat based on it's tech, and maybe MS is willing to subsidize those cards to some degree. I also can't help but wonder if MS assumes most will just transfer over their existing external HDD's, or upgrade to a larger one based on the much cheaper market prices.

The cost over time also needs to be taken into account. A proprietary card only comes down in price a lot if MS keeps subsidizing it, or if they sell a boat load of consoles, while also convincing many to buy 1 card or more. Mass market gen 4 NVMe's will naturally drop in price much quicker, which also means lower prices, or faster speeds, and higher amounts of storage for the same old price as years go by.