Mike, if you are talking about restarting the numbering across the whole line as a different thing than restarting individual titles, then yes, DC has only done that twice. But DC has certainly restarted individual titles many other times. Justice League (or JLA) has restarted several times. Also Green Lantern, Hawkman/Hawkgirl, Green Arrow, Flash, etc.
I am having a hard time thinking of ANY time when Marvel has restarted ALL of their titles at once. Even this new MARVEL NOW thing leaves a few of the older numberings intact, if only because they restarted within the last few years. But certainly I do agree that each individual Marvel title has been restarted so many times, and in such nonsensical ways, that it has become a running joke.
But I wouldn't say, just because DC does it somewhat less often, that this constitutes a concrete difference between them and Marvel. Jonesy's point about them both aiming for the same market is still quite valid, I think. They both make fitful attempts at reaching wider audiences, but nothing really convincing or confident.