They're far more similar than you think.

http://www.vgchartz.com/yearly/2012/Global/

Info here. Well would you look at that, both down exactly 8%.

A separate comparison for PS3 and 360 please.

Anyway I'm sure both platforms will go up this year. GTA V + COD MW4. That's 2 games right there.

Sony likes to announce things early

The PS3 sales will be nowhere near that of the PS2 sales ( when the PS3 launched ) .. The PS2 had a 90 million console lead over 2nd place console ( Xbox 1 ).. and the PS2 had all the games and all the best games .. The Sony fanbase while loyal has shrunk alot to just those who really are loyal to the PlayStation Brand name.  The PS4 looks like a console that will leave the "updated Cell CPU" idea behind because the new PS President understands the majority of the developer base has to spend much more time making games for the PS3 which equates to more money - often not improving in quality by much.. If the PS4 does launch as it seem it will - with a structure closer to the Xbox ( more like a PC ) Sony will be basically admitting Cell was a mistake.. Sony went from a 1st place 90 million console lead - to what remains of thre loyal fanbase - arguing when and if the PS3 will finally overtake the Xbox 360.. most of the fanbase has said over the last 4 years that it would happen year after year.. but if sales decline like it looks they will quickly for both consoles - there is little chance of this - but even if it does - Sony is more considered about overall profitability of the PlayStation division .. This generation Sony ( overall ) looks to be the least profitable.. consoles sold maybe what consumers look at - but Sony shareholders and board members care more about what console makes the most - and it still cost more to make a PS3 then the other 2 consoles by far.. maybe d/t bluray and cell cost

About 8 or 9 million, there will be a price cut which will help, but a PS4 announcements going to slow things down a lot.

Personally, I think this is a sign of multi-console/platform ownership more than anything else ...

A significant portion of people who own a PS3 also own a XBox 360 (and vice versa) as well as a Wii, PC, Nintendo DS, 3DS, PC, Wii U, Tablet, Phone and/or iPod and are only purchasing games that are particularly interesting to them. The features of the PS3 and XBox 360 that made them the go-to console for so many people a few years ago are "old-hat" now, and people are seeking out new game experiences where they can get them.

Thanks for the info, great stats!

Could it have anything to do with digital sales?

Here is the separated analysis everyone was asking for.  I copy and pasted the exact numbers from the charts, so you will notice 2005 looks a little different because of the rounding TheSource did.