Steam – Do Mac Steam keys work for PC

The differences lie in the services that Steamworks and Origin offer. If you are only playing a game in singleplayer and you have no need for anything special, then they should both be identical experiences. However, if you do care for extra community features provided by Steam/Origin, ask yourself several things such as the following:

Does Origin or Steam offer a better community? Does Steam or Origin have better support for achievements for this game? Does one support cloud saving while the other does not? Am I more invested in Steam or Origin?

Steam has a larger catalog and it's been around for longer, which means it may be worth investing your online presence in Steam rather than Origin. However, if you're happy with the catalog that Origin offers and you want some of the games that are on Origin but not Steam, Origin may be the way to go.

It really depends on how much you care about the external features provided by both services. It's likely better to primarily use one service, so if they are both equal for a specific game, buy it from the service that you have a larger presence in.

As a general rule, games that use Steam for distribution and DRM (or otherwise register on Steam) will install some content from the disc then update (or download) further data. This absolutely relies on the game being a Steam game - if it doesn't require Steam (or a Steam account) on the box, you probably won't be able to register it on Steam.

You can see a list of the games that use Steam for this purpose here, though it doesn't appear to be exhaustive (for example, not including CoD:BO3 which does seem to use Steam).

The Division (another game you mention) is a game published by Ubisoft, who these days seem to sell games on Steam, but physical copies with keys for uPlay.