You could just refund it if it doesn't work well for you. GOG are usually pretty generous

Depends on what you’re looking for. On Steam you get stuff like Steam Input, and ofc having it be tied into the Steam ecosystem, which depending on how you play pc can be a big deal or not so much. Plus if you plan on playing on Deck, it’s a bit easier if you own it on Steam.

With GoG it’ll be DRM free, which for many people is a massive deal. Basically once it’s downloaded it has zero ties to GoG, meaning it’s yours and yours alone, you can do whatever you want with it, back it up, turn off your internet and play it whenever you want. You can even download it from the website without having to install the GoG client.

Plus through GoG you can easily install the Fallout London mod, which may be a nice bonus depending on you.

Ultimately I’d say GoG unless you’re heavily invested into Steam and would make use of the integration with the ecosystem.

Steam versions of games tend to run a little better, and also benefit from things like Steam distributing pre-compiled shaders for the games. There are also some cases where non-steam games will require you to install specific windows components through wine for the game or in-game media to work.

Overall Fallout 4 should work, but without actually trying it I can't say if it will work without tinkering or not.

Edit: did some searching, sounds like it mostly works, but you may have to manually install xact_64 to get sound working.

If you want to play Fallout London, get the GOG version. It's extremely easy to set up. The steam version needs you to revert it back before BGS broke it with the next gen update. It's a pain.

Why you shouldn’t buy FO4 on GOG: On Linux it’s a bit more work, installing the game via steam it’s just one button and you are good. GOG you need a third party game manager like Heroic or Lutris. From there you can add it to steam, you’ll also want to download art as the ones provided by lutris are low res.

You’ll also have a hard time with online saves as you’ll need to also install GOG galaxy, which isn’t fun and is very buggy.

That said, from an application perspective, it’s running on Proton regardless, so it’ll run the same. And since the folders are easier to find (more structured like windows), I personally find modding in general easier.

The reason you want to buy the GOG version is that it’s drm free and yours to keep. No launcher required. Not something you’d care about on a steam deck, but on a PC it’s nice to have.

I try to buy things on GOG when I can just for the sake of diversifying my dependence on one company.

There are plenty of guides to setting up Heroic Launcher on the Deck. Once its set up, it's easy to install games.

I've found GOG games to run perfectly fine, and cloud saves work perfectly.

Lastly, I saw some other people saying GOG doesn't have the latest version of this game specifically, so definitely check that before buying.

Last time I checked (and it's been a few months), GOG hadn't updated their version of FO4 with the "next-gen" update that came out early this year. That may be a good thing or a bad thing depending on your perspective because supposedly the update breaks a lot of mods but also is supposed to increase performance.

As much as GOG/CD Projekt have more than their fair share of problems, usually their versions of games work, can be preserved, don't require as much bloat, launchers included, and usually don't require 3rd party validation. And like others said, besides Wine and related, and installing through Steam as external games, you can also install stuff very easily through Heroic and the sort. So I'd say it's the better option indeed.

I don't how easy it is to install non steam games. I know it's possible but takes some more messing around.