Without question the 360. However. And this is a big however. I believe that 50% of 360's died to RROD and this bumped sales significantly making the console appear more popular than it was, I can't find it now but I used to have solid evidence that the failure rate was slightly above 50%. I lost one, everyone I knew who had the original model lost at least one and one fool I knew bought the console four times (used 3 times) after me trying to get it into his skull to just buy an elite model after the second failure which I believe didn't have the same failure rate. So, I believe Xbox has stayed as popular as they have ever been up until this generation where they seem to be slipping off. I don't believe there ever was a point where Xbox was winning the 7th gen apart fron the first two years where they had the early start and Sony stunned release in regions. I belive PS3 caught right up to them much sooner than the numbers implied.
Found on some scource not sure if it's right ai haven'tchecked into it:
54.2%
Microsoft's Xbox 360 has an overall first-time hardware failure rate of 54.2% among its readers, according to a report by print magazine Game Informer in its latest issue -- and 41.2% of those users were said to have multiple failures.