Anyone who starts quoting install bases has no idea why it was so close. The reason it was close is because of the exclusive joker content. A lot of people with both systems went with the PS3 version just because of that

Even without knowing what both version sold, it's possible to see by how much % the xbox 360 sold more than ps3.

45% - 55% can be equal to 45 - 55 units.
It does not have to be, but it doesn't matter what numbers we use, if the number does match the % correctly.

To check how much more % 55 is to 45, you'll only have to split 55 with 45. Which is 1.22.
1.22 = 22% more sold in favour to Xbox 360.

^^ yup exactly
equates to every 9 PS3 version -> 11 360 versions are sold

The only people who are going to choose between the PS3 version and the 360 version are those who own both consoles. I'm guessing dual console owners are not that many in the wider gaming public (lets go with 10% to stay with the theme of the thread).

It's possible that having the Joker as playable on the PS3 makes the game more appealing to PS3 owners than 360 owners, hence the PS3 version attracting a larger % of the install base than the 360. I would imagine that among those who own both consoles the vast majority will get the PS3 version because of it, but that would only represent a relatively small proportion of the total PS3 sales (assuming 10% dual ownership).

Let's make it easy on us and say that across both consoles AA sold 100,000 units with a combined install base of 5.87 million, this represents an attach rate of 1.7%. Assuming 10% dual console ownership, let's make the number as big (significant) as possible and say 10% of 360 owners also own PS3. 10% of 3.7 million = 370K dual console owners in the UK, 1.7% of 370K = 6301 dual console owners buy AA out of a total of 100K buyers. Meaning 6.3% of AA buyers are dual console owners.

Now lets assume all dual console buyers purchase the PS3 version. What sort of attach rate is needed among PS3 only owners for PS3 to get 50.1% of total market share? 50,100 - 6301 = 43,799. 43,799/1.81 million (total PS3 owners - 370K)= 2.4%. i.e. PS3 attach rate needs to be 2.4% for PS3 to gain 50.1% market share. Conversely the 360 attach rate would need to be 1.5% to only garner 49.9% of market share. That means the attach rate differential between PS3 and 360 would need to be a massive 60%. i.e. AA would need to be 60% more popular among PS3 only owners than 360 only owners.

This is based on only 2 assumptions: 100K total sales and 10% dual console ownership. make different assumptions and you will get slightly different results.

Conclusion: the choice of dual console owners will overcome the inherent lead that the 360 install base provides without a massive difference in popularity between the PS3 demographic and the 360 demographic. In fact without crunching the numbers I would guess that with relatively similar popularity (which I would expect from the nature of the game) the significant advantage PS3 gains among dual console owners (I'd say at least 80% market share among dual owners, possibly higher) would pretty much give you the % figures quoted in the OP.

One question is: does the playable joker represent sufficient reason for a 360 only owner to go out and buy a Slim, or someone who is thinking about getting an HD console to come down on the side of buying PS3? I don't think so. An HD newbie is going to look at the totality of the games they want to play and choose the console that gives them the most games they want to play, so the Joker might be a tie breaker. Without many other PS3 exclusives that are of interest to the current 360 owner the Joker is not worth forking out the money for a Slim, though it may be that final nudge they need to finally take the plunge and become a dual console owner. How many people will fall into those categories of potential PS3 buyer? Not many, if any.

I imagine that this will change when the game sales are complete for the 'Others' region! Hard to tell though so we will just have to wait and see!

we can see from this that the ps3 users in the UK must be super hardcore gamers. theres a huge userbase difference in the uk and the 360 version only sold 10% more.

Isn't the real story here that the Joker DLC helped the PS3 to a higher attach rate for the game?

yeah and with the 'joker' exclusivity it can get only better for PS3 sales

^^
I think that's been mentioned a few times. Although it's hard to be sure how much difference it really made.

I doubt many 360 owners got a PS3 just for Joker, and I'm pretty sure few PS3 owners go a 360 to play it without Joker. Of course The Joker may have swung those with both consoles, but the key question is what percentage of twin HD console owners are there vs only one console?

If a fair percentage of people have both then it's more likely the DLC tipped the scales, if the majority only have one console then it's hard to imagine it made much difference.

I guess whichever way you cut it the attach ratio favored the PS3 in UK for this title.

I'd imagine the PS3 version is performing so well compared to 360 (Okay in the UK it favoured 360 but overall it's very close and maybe ahead for the PS3 I think?) is because of the price cut. Alot of people are picking up Ps3 at the moment, and the game has launched perfectly alongside this - I've already seen alot of stores here in the UK doing a £249.99 Ps3 Slim + Batman deal.

360 version will show stronger legs though I reckon, all in all though Batman:AA is looking like it's going to be huge. I honestly think it could be a sales monster, end up third to MW2 and AC2 on the HD consoles holiday sales front.