One of the perks of Steam, is the ease of continuing from anywhere.
Most games on Steam with more than ten cents worth of effort, support cloud saves. Most that don't tend to be very old, or games that shouldn't. Which makes it pretty easy to continue from another machine, or even the same machine from some future reinstall of the game. Many games on Xbox also support cloud saves, and it's usually less famous titles that lack them, like indie titles.
At least when you've got a solid graphics card, and aren't struggling to run the game to begin with, Steam's in home streaming actually works great. So transitioning from /dev/desk to /dev/couch is more to do with input devices.
Microsoft's Game Pass is pretty sweet, and ultimate makes sense if you were already paying for Live. But the trade off I think is the portability.
When I play a game on Steam: principally, I give little mind to whether I'm playing from my couch or in front of my computer. The decision is typically driven by how much precision mouse/keyboard work is required. The only game that's been otherwise is Final Fantasy 15, as my CPU struggles to run it locally, unlike 99% of my other Steam games.
When I play a game on Game Pass, principally my thought is "Do I want to play at my xbox?".
As much as I applaud Microsoft's record and stream tech, I really love that they made it available, the truth is that I find the stream quality from my Xbox to my desktop to be inferior to my 780 GTX to my SteamLink over the same network and locations. There's more visual glitches and even set for quality, the encoder can't best the encoder on my nVidia card.
What would really make the PC side of that coin mean something, is if it were possible to share the same saves between my desktop and my Xbox. I.e. the decision would be like open Outer Worlds on my desktop, and continue from the same save I made on my Xbox. I'd call that a win.
By contrast the decision works out that I started playing on my Xbox, and need to stream to my PC if I want to play at my desk. Which means a loss of image quality, and the occasional wtf/freeze/lag; on the flipside Outer Worlds seems to do that less often than Halo 5 when I stream.
Likewise, I don't think Microsoft offers the inverse. I.e. that I could stream my desktop to my Xbox, if I had started with the PC, I'd not be able to stream to my Xbox. Although it might be possible to horse wrangle something with my SteamLink. By contrast, Steam's streamy goodness is basically from anything to anything, especially when you account for needing a Direct3D PC for most games anyhow.
Thus, I am finding that Game Pass is very worth it for the Xbox side of the catalog. On PC, it's more like a "Meh", because the only benefit I'm really seeing there is good odds of playing on desktop with a mouse, a game I wouldn't want to play on console with a controller. To be fair though, my decision was based on the cost comparison of Game Pass + Live versus Game Pass Ultimate; that is to say on the dollars required.
Beyond the lack of PC <-> Xbox crossover, I'm finding Game Pass to be very worth it. For a while, I've actually considered dropping my Live subscription because Games with Gold doesn't bring that many games of interest down the pike, versus how little multiplayer I tend to do on Xbox. Where as Game Pass delivers the content, and probably curtails much of the need to buy games outright.->
I'm also pretty sure that if Valve offered something like Game Pass on Steam, I'd probably hand Gabe Newell my checkbook and be done with it, lol.