I think there are a few very clear points to mention:
1. Both systems are in very high demand.
2. Both will likely sell through all they can produce for the holidays
There are some indications that Microsoft might have been able to produce more units, but there's no proof at all... just some evidence. There's also evidence that Sony may have produced just as many, but simply opted for different allocations for each country... but there's no proof as to who's selling more, which console is in higher demand, and/or which console has more world-wide sales... at least, not that I'm aware of... but I'm happy to be proven wrong. :-)