How many versions of Xbox 360 consoles exist, and what are the differences between them?
Right now there are 3 Editions on the market:
Now the Slim is replacing the Elite, so that one will be phased out. There is also plans for a slim arcade version which will phase out the arcade. As a result neither the Arcade nor the Elite are currently in production.
The major difference between the Elite and the Arcade is the presence of a Hard drive. While the Arcade does have a small amount of on board memory, it isn't much.
Additionally, the Elite comes with a Headset and Ethernet cable.
The new Slim also comes with hard drive, headset, but lacks the Ethernet cable in favor of built in wifi (which must be purchased separately for Arcade and Elite).
You can still find the standard Elite with 120GB HD or 250GB HD and 1 or 2 Controllers (all others come with just 1 controller).
It is worth noting that the Slim is branded as Elite, even though it is different than the current Elite you can find on the market. The noticeable difference is the slim being smaller and having a less rounded exterior.
Right now, only the "S, 250BG" is in production.
The "Elite" version came in two sizes "120 GB and 250 GB" but were mostly similar otherwise.
Hardware-compatibility wise, the systems we all very similar. Microsoft has stated that the "S" series contains almost identical hardware to the "Elite, 250GB" because no game is pushing the limits of the hardware yet, even at 1080p.
In 2013, there are just two versions of the 360 sold - both are classed as the "Xbox 360 S". Both models are identical in appearance, one has 250GB internal storage and the other 4GB. There are also other variants avalible as promontional packs such as a "Halo: 4" edition with a different colour scheme and start-up sound, or a "Gears of War" one with a special red print. Both these versions come with 320GB storage.
Both 4GB and 250GB models appear to have the model number of 1439. I just had a look at the rear of mine and there was no way to distingish if it was a 250GB or 4GB model.
All consoles sold now have HDMI ports, Wireless inbuilt, and a connection for the Kinect. I would expect they would stay like this until the next generation "Xbox 720" comes out.
Most other editions are getting phased out, but the new Kinect-ready edition is the only one that they're planning on keeping around. It's got a 250 gb HD, and built in Wi-Fi. Other previous editions don't have both of those features.
As per the above image, there are only 7 different Xbox 360s out there.
Note that the real differences between the XBox 360s are only memory size and color schemes. Having more memory allows you to buy more games from the marketplace, etc.
What it comes down to is that the only thing separating today's Xbox 360s from the first Xbox 360s are the memory size and color.
For me, I never bought the newer XBox's out on the market. I stuck wit the XBox 360 Core, one of the very first to come out.
The various versions (Arcade, Pro, Elite, 'Slim') are mainly packaging differences (apart from the new Slim hardware).
There are actually multiple hardware revisions starting with the original Xenon which was the loudest, most power sucking version.
When the Elite first debuted, it had the newer 'Falcon' hardware which had a smaller cpu and ran on slightly less power and later all Pro/Arcade versions were released with this same hardware.
Subsequent revisions reduced the gpu size and overall power consumption leading up to the 'Slim'.
The 'Slim' is really the first major revision of the console, I would say (obvious by the new form factor, multiple usb ports, built-in wi-fi, etc), and running the smallest cpu & gpu and lowest power consumption by far.