I think that the easiest way to answer the question would be to break down and examine each console's prior performance and current situation by region.
In the United States, the 360 has been comfortably ahead of the PS3 for quite some time. The PS3's slim model was a huge boon to the console sales-wise, but since the 360 slim model was introduced to counter it, it has been defeated quite soundly month after month.
With the introduction of the Kinect, which has, like it or not, become a phenomenon in this region, the 360's sales potential has been bolstered significantly. This is in stark contrast to the Move, which has failed to make much of a splash or much of an impact at all in the region.
When it comes down to it, I'd estimate that the 360 will outsell the PS3 2:1 in the United States in 2011.
In Europe and the "others" regions, it's not quite as easy to speak of the market as a whole, as taste, culture, and purchasing activity varies so significantly from country to country. Certain countries, such as Great Britain, strongly prefer the 360 to the PS3, as shown by their purchasing activity. At the same juncture, other countries in this region are essentially a single HD console market, strongly favoring the PS3.
Before the introduction of the slim 360, the PS3 was beginning to comfortably pull ahead. This gave the 360 an advantage in the region for a few months, but after the initial sales boost it appears that the PS3 has begun to win the region by a comfortable, though not staggering amount.
It should also be taken into account that the Kinect hasn't taken off nearly as much in this region as it has in the United States, for whatever reason. The sales boost from Kinect certainly isn't minimal or insignificant by any means, but it's not as large of a factor as it is in the United States. In fact, considering how much more popular the Move is in this region compared to its sales in the United States, it may even be enough to bolster the PS3's sales to the point where the Kinect boost is offset entirely, if not surpassed, strictly speaking of this region.
As a general rule, the 360's sales seem to be approximately 75% of the PS3's sales, without any major releases influencing anything.
When it comes down to it, I'd estimate that the PS3 will outsell the 360 4:3 in this region in 2011.
When it comes to Japan, it's pretty clear at this point which way the numbers are going to skew, for one reason or another.
The 360 slim model, while boosting sales by a very healthy amount percentage-wise, doesn't do much in the way of stacking up when it comes to competing with the PS3. We're talking up from 2,000 to 4,000, which really isn't much when competing with the Playstation 3, which often reaches 40,000 or more sales per week.
When it comes to the Kinect, while it's performing very well for an Xbox product in Japan, that's really not saying much. While it's had a sustained period where it's been above 10,000 per week, it hasn't done much in the way of boosting 360 hardware. Then when adding Move into the picture, any momentum gained by the Kinect are likely not only offset, but far surpassed.
With that said, this region seems to be trending more and more towards handheld consoles and farther away from traditional consoles, and likely won't make too significant of an impact on overall sales when looking at the big picture, despite the PS3's absolute dominance over the 360 in this region. While owning the Japanese market is certainly a nice asset for Sony and while the overall boost certainly isn't insignificant, in the end, it's not going to ultimately decide who wins the console war. The 360 doesn't need Japan to win, though it's certainly a handicap.
Overall, I'd say that the PS3 will outsell the 360 by 10:1, if not more, in Japan.
A number of other factors need to be taken into consideration, such as:
-The exclusives that each console is launching in 2011. When it comes to announced exclusives Sony certainly has the edge right now, but Microsoft always keeps its cards close to its chest when it comes to their release lineup. The effect of Gears of War 3 and Forza 4 shouldn't be underestimated, either.
With that said, at this point in the console generation it's unknown how much of an impact exclusives will have on sales. It's likely that most people who would buy a console for a single game already own the console that they're interested in, and one single game likely won't change that, especially considering how almost every exclusive game that's released is a sequel to a game that's already had an interation on the same console.
-Price cuts could certainly change the game, but Sony is at a significant disadvantage in this regard. The company is hurting for money as it is, especially after the PS3's hemorrhaging money in its initial years, and they need to squeeze every penny that they can get.
Sony is extremely unlikely to make a price cut unless Microsoft initiates one first, and even if Sony does take the initiative and make the price cut first, Microsoft can not only comfortably match it and still draw a profit, but beat it and still draw a profit. Sony's truly at Microsoft's mercy when it comes to pricing.
-The effect that Kinect (and to a lesser extent, Move) will have in the non-Christmas months. Were the Kinect's massive sales a byproduct of the Christmas season, or will it follow the Wii's lead (in recent years) and be down significantly in the non-Christmas months?
Another variable is how much support that the Kinect and Move will get, and the type of games that are produced for them. There's a lot of potential there, but will it be ultilized to their full extent, or will companies be content to continue pumping out minigame compliations? Time will tell.
When it comes down to it, I'd be prone to say that the 360 will comfortably, though not significantly, defeat the PS3 in 2011. Riding on the momentum of extremely strong US sales, its newly found casual appeal with Kinect, a decent exclusive lineup, and the slim model, I wouldn't be surprised to see one of the 360's strongest years ever sales-wise. Taking all factors into consideration, in my estimation, the gap will grow.
EDIT: Just to throw a prediction out there, I'm going to estimate that 15,500,000 360's will be sold, and that 14,100,000 PS3's will be sold in 2011.
