+ The latter is clearly superior in technology (or content) to the other.
+ The latter makes user happy by giving them real value, whereas the former focused on milking the users for revenue.
+ The latter made promises to the users (Google: "don't be evil", SO: "contents are the community's property") and the users liked it.
+ Last but not least, "the competition is only a click away" (Google). "You can start a SO competitor in a heartbeat" (SO).
So far so good. But guess what happened to Google? They got good. They got big. They were no longer satisifed with being the king of search. They started Plus. They started saying "If you don't want people to know what you do, you shouldn't do that anyway". They now want your data to be shared among their properties and you cannot opt out. They got jealous of Apple. They got freaked out by Facebook.
I don't doubt Google started with a conscience, and a genuine focus to build a better search engine. They succeeded. Wildly. But except for the most hard-core Google believers, I doubt that many people still trust their "Don't be evil" mantra in its absolute. Frankly, do people even say that with a straight face outside of comparison with Microsoft?
I love SO and believe in the integrity of Joel and Jeff and others. You guys really rock. But time will change. Tide will change. A tidepool that is fun for little kids could become a fatal trap the very next day (sadly, this happens often). So please keep the warning in mind.