MIK3K: I think it is more the dev than the service. There are some games on steam that never get updated or are an update behind everyone else (making them incompatible for online play with everyone else). There are a couple of games that are getting updates on steam before the other services. I think there was one game that the dev said in the forum they were just concentrating on the steam updates.
It all depends on what the dev does and who and when they submit their updates. GOG and Steam don't control when they get the patches. It's pure luck where you buy your game and how that dev feels about updating that service.
I buy a lot of games on desura and gamergate. I hate seeing the updates on desura and waiting and waiting for the gamersgate update. I actually had to remind a dev one time not to forget the people that bought from his personal website when he was updating desura :/
Well...