Well if you already have a pc and 1070 is pretty powerful. I would rather look for a way to hook up to the TV through moving or long cable. Your power isn't much behind a series s unless you have a crappy cpu. Then playing on that setup and watch over further development. can't imagine a huge difference unless you have a big ass 4k TV and sitting right in front of it. Going that way you can always change your mind, buying cheaper series x after some time, changing to ps5 (because of great exclusive while covering xbox exclusive on pc) or upgrade pc in some years if hardware gets cheaper and more powerful then series x.

Each platforms have they strength. If we talk about Teraflops, well, you know that the frequency on PS5 is not fixed, even Cerny said the real sustained performance will be get a couple of % points lower sometimes, Some people speculated that the real performance of PS5 will be 9.2 Teraflops, but lets get nice and consider it will be 10. On the other side XBOX Series X has 12.15 teraflops.  So the difference there will be 21,5% there. Its not a great difference but there are many times that a GTX 2080 doesn´t get to 4K60, So the extra power is nice to have. There will be several games that reach that resolution easier than on PS5.  

But teraflops are not the whole story. The specs are balanced, you have a 560 GB/s bandwith 320 bit bus for the GPU, compared to 448 GB/s 256 bit bus on PS5. That is a 25% advantage. 

Also PS5 has 2304 shader units / 144 texture units vs 3328 /228 in the Series X. That is 44% more shading units on the X and 58% more texture units. That benefits Ray tracing capabilities , despite the clock speed advantage of PS5. 

So  there you go. 20% is a fact. And as consoles do 30 fps or 60 mainly if you don´t have a freesync TV, The Series X will handle 60fps more times than the PS5, or will get lower quality graphics, or will get less dinamic resolution.  As New consoles are much closer to PCs, the 3rd party developers will increase graphics depending on the capabilities of the Consoles. 

On the SSD, For multiplats, they have to work on PC, and there are only a few that have nvme drives, and fewer with 5 GB/s ones. So I guess that most third party will get benefits for the SSD, but not as often as we would like. PS5 exclusives are the games that will getting benefits on that. 

As I prefered my old PS4 for 1080p, as it reached that reso most of the time, This time I think that the Series X will be a better value in that regard. 

Also with games like Warzone with more than 200 GB, and others arround 100 like Destiny, RDR2 and so on, I don´t like to have only 665 GB available on my system when I have more than that on my PS4 pro (arround 800) and even that is not enough for my taste. 

First, putting every people from a country in the same bag is offensive and doesn´t have anything with the post. You should respect people from other countries.

Second if you look at digital games on Xbox Argentina Store, you will see that now F1 2020 is 1000 AR$ and 60 USS on Sony Store. 

60 USS is  arround 8400 AR$. That´s 8 times the difference. 

Now If I want to get the next Dirt 5, same pricing. 8 times more expensive. 

https://www.xbox.com/es-AR/games/all-games?xr=shellnav#

the next Call of Duty? 3000 on XBOX and 9800 AR$ on PS5

Gears 5 is 1749 AR$ And TLOU2 is on Sale at 40 USS. 5600p

So It varies between games but I would put the average between 3 and 5 times cheaper. 

The price of the dolar is arround 80AR$ but then you have to pay 30% and then 35% more (Country killing Taxes). The unofficial dolar is arround 180 AR$ now. 

So I guess for 1 PS game I can buy an average of 4 Games on XBOX. And that is without considering Game pass. 

Its a nice graphic card, I can play many games at 4k  at arround 35 fps. And almost all at 2K 60 with tweaks here and there. I have to check specs, but I think it might be faster than a Series S. The main reason for a Console is playing in my small bedroom while resting. Also the 1070 doesn´t have ray tracing, So despite It won´t be a game changer, its nice to have a Series X, specially with a 4k TV. 

Edit: GTX 1070 is better than Series S Overall. But I guess not for much, Architectures are different to compare side by side here and RDNA2 is more modern. Some people say that an XBOX Series S wil be arround the Same performance of ONE X. And One X is arround an AMD RX 590 Which is 80% of a GTX 1070.

A GTX 1070 is arround 20% slower than a GTX 2060 super, So I would imagine that a 1070  will be middle road between a PS5 and a Series S in real world performance without Ray tracing. 

GTX 1070 Specs

6,5 Tflops, 256.3 GB/s BW, 120 TMU, 64 ROPS.

XBOX Series S

4 Tflops, 224 GB/s BW, 80 TMU, 32 ROPS.

Also As I said because of actual pricing in my country, is cheaper for me to buy a Series X and all the 3rd party games, and afterwards a PS5 for only the exclusives than buying a PS5 and all the games on the sony store. 

I calculated that buying arround 12-15 games on XBOX ARG Store instead of on Sony ARG store, the money I saved would be enough to buy a PS5. 

The value of GamePass compels you

I've had a Nintendo console, since the NES days, but since the PSone came out Play Station has been my second console of choice. I have never owned an Xbox, not because I think it's a bad console, I just prefer the other two. I do enjoy playing Xbox games at my brother's house. As for next gen consoles, this is the first time I'm feeling a little inclined to go with Xbox. I'm going to wait to see how things result, but I might abandon PS5 in favor of the XBX

I love how despite OP never mentioning GamePass once, and comparing individual game PURCHASE prices,
so many people here are still absolutely sure that GamePass is the fundamental reason behind OP's choice.

It sounds like MS has different set up for their digital store, and Sony isn't taking advantage of same approach.
Would be interesting to learn what is the basis of that, honestly with so many taxes on the entire ecosystem,
Maybe MS is "licencing" entire store/games to local subsidiary rather than "importing" each game, or some such?

It does, otherwise there would be no reason to change consoles for new ones. The CPU and SSD of series S has similar specs, so what developers will do is just the same as they do with PC graphic parts, The game will be the same but running at 1080p-1440p on Series S and 2k-4k on Series X. They will take advantage of the hardware, if not 100%, 90%. 

Im not forgetting about the I/O, I just think that only Sony Studios are going  to take advantage of that. I don´t see third parties making the game with two different stream management or more, they need to make the games work on PC too. And you have a world of difference on HDDs and SSDs there. 

Lastly, Im not an XBOX fan boy, I´m closer to a Sony Fan Boy if I have to choose, mostly because the Awesome quality of Studios and I have almost all the exclusives on my ps4 pro, so yes, exclusives will be awesome on PS5 not only graphically but artistically. I´ll play them later down the way. For the rest of the games, they will be better on XBOX. 

The thing is 

I love to have my game collection. I don´t want to be attached to a service. I like to have my games  and play them when I want. There are plenty of great games that are not on Gamepass. The good thing is that I can buy my favourite games cheaper, and play several other games that I normally wouldn´t buy the months  I pay for the service. Or on the other side, pay for Gamepass for some months, play plenty of games and then buy the ones that I really love to keep.

I think as Microsoft has offices in my country, they probably are licensing othe games. Or they just import them for less money. With Microsoft I pay with my country currency. With sony is like importing the games, I have to pay USS dolars.