What important differences are there between the various online game distributors? [closed]
Solution 1:
Steam has two major advantages:
Steam Sales
(edit: this is less true these days, other online stores now have huge discounts regularly too) 75% - 90% off most major titles within 6 - 12 months of release. There is nothing close to the deals steam have, not on online shops, not in bricks-and-mortar shops, not even second-hand.
Valve's reputation
Valve have proven time and time again over the years that they are "the good guys". They make a lot of effort to do right by their customers. So I trust them (more than any of the companies you listed) to not lock me out of my games if they can help it. If Valve ever got sold and decided to cancel Steam forever, they're the company most likely to secretly release a hack or something to keep my games running.
They are also extremely profitable, thanks to their excellent games (I mean the first party titles like HL, L4D and Portal), and to their excellent business model. They are the digital distribution company most likely to stay in business forever.
Solution 2:
Two words: Humble Bundle
Humble Bundle (previously Humble Indie Bundles, site: https://www.humblebundle.com, Wikipedia article: Humble Bundle) is an online digital storefront for games. It offers limited-time bundles of games and now a persistent storefront. Some of the site's most distinguishing features is the site's showcasing of games by new indie developers, its multiplatform support (including Microsoft Windows, Mac OS X, Linux, and Android platforms), and how the site's offerings support a number of charities (including Child's Play, the Electronic Frontier Foundation, charity: water, the American Red Cross and the Wikimedia Foundation).
The site's most notable feature probably is its Pay-what-you-want pricing for its game bundles. Most bundles have a theme (horror-themed games, strategy games, games from a particular developer, etc.) and offer a small group of games to everybody who purchases the bundle at any price. The bundles usually then include two or three tiers so that all people who pay more than a certain amount get not just the main bundle, but the additional tier rewards for all tiers up to that price point.
After buying the games through Humble Bundle, many games can be downloaded DRM-free some games also include codes to unlock the game in Steam, Uplay, etc. The sites' makers know how much of a problem DRM can be to gamers, even when the game was bought legitimately. As such, Humble Bundle tries to offer games with much less hassle than many other digital distributors.