I only use Steam because some games require it. Which is bullshit, but I'm unwilling to forgo certain titles like Skyrim or Deus Ex. GOG is faster and easier to use, has better customer support and of course no DRM. It also does not save your credit info which is the best defense against hack attempts. I'd buy every game on GOG if I could, and no games on Steam.

Gog , two words: drm free

I use GOG for old games and Steam for new games.

GOG takes much more care with old games, making sure they work on todays hardware and giving extras where possible.

Steam has a more convenient setup for new games that release multiple DLC's and usually require regular patching.

GOG isn't a program, and that's a plus.

With an infection.

I use both. I tend to favor GOG for single player and older games, games that I've wanted to play but only within the past 5 years (Yes, I've been here that long...shit.) have been able to procure legally. It's simple, I like having the installers where I can move them around and whatnot, and the DRM-Free is amazing.

Steam...well, Multiplayer games. Most of my friends live in other parts of the country so having good multiplayer games is a plus. Steam allows us to easily join each other and it's really not too much of a hassle. The benefit for auto-patching some games is nice (again, a benefit for MP games), and the cloud saving for saves is a nice benefit as well (Especially with me only 2 weeks into using a new computer, saved my ass in a few places.)

On GoG you feel welcome and its DRM free.

On Steam you've the convenience and the prices.

GOG goes toe-to-toe with Steam on pricing deals.

And with the extras on gog, you're basically getting an all round better deal.

I would never buy a game on Steam that's also available from GOG, even if the GOG version is more expensive (which they usually aren't), since GOG gives better value for money over time. GOG personally ensure the games they sell remain compatible (going so far as to introduce a money back guarantee) whereas Steam leaves it up to the publisher/developer.

Those using Mac OS X are also better off with GOG since there are now OS X packages included for many games that are still Windows-only on Steam and elsewhere.

If you like DRM, go with Steam.

For some reason the title made me think of Ultimate Showdown of Ultimate Destiny.

When you buy a steam game its still theirs, its like your renting on a permanent basis. Steam can club you and take away all your games at any time, even if they don't its still unpleasant knowing they could. On GOG I download a game and put it in my tower and I have it for whenever I want it its mine.

GOG is free to join, won't install anything on your machine, and will even give you a bunch of free games to play and keep for your own.
Why not try it out for yourself?
Bet you'll stay around if you do. ;-)

GOG:
No client needed though downloaders are made available (handy for larger installers)
download-install-Play (not download-install-confirm-Play or Install-download-confirm-Play)

I don't always use Digital Distribution but when I do, I prefer GOG.