Note: This review is primarily for the newly redesigned Xbox 360 (S) 250 GB but to make a comparison between this console and the PS3 Slim, I will to some extent be doing a dual-review.
The new Xbox 360 (S) is Microsoft's answer to Sony's PS3 Slim. I will start by describing the similarities that represent the two new models:
Both newly redesigned versions of the consoles now come in a slimmer, lighter, quieter, and more visually appealing form factor (360 = Matte to Glossy (black), PS3 = Glossy to Matte (black) finish). Both consoles are now the only models in production for their console line (other remaining models are being phased out at lower prices). Both consoles also use a 45nm-based chip process that allows for their smaller size and whisper-quiet operation. Both the Xbox 360 (S) and the PS3 Slim are priced at $299.99 (US).
The Xbox 360 (S) is different from earlier models in that it comes with the Valhalla motherboard via the XCGPU (this is a GPU, CPU, and 45nm eDRAM all integrated as one) which allows for the new 360 (S) to not only be smaller and quieter, but also eliminates the issue of overheating (cause of the infamous Red Rings of Death) that was prevalent in earlier models of the Xbox 360. In addition to this, the new 360 (S) introduces 5 USB ports (3 more than before), 1 proprietary Kinect-ready port, built-in 802.11 b/g/n WiFi - the fastest built-in WiFi of any console (built-in WiFi was not available on earlier models; adapter was required), and a TOSLINK S/PDIF optical audio connection (not available on earlier models). With the capability of using Flash Card devices as support-memory for the Xbox 360 (available through an update in April 2010) has led to the extinction of those unnecessary and obsolete memory-unit ports. Part of what makes the new 360 (S) slimmer is that it has a more-compact, internal-but-swappable 250 GB hard drive that unfortunately can not be used with older models of the Xbox 360 (though there is a way to transfer memory from one console to another via a transfer-kit). Part of what makes the new 360 quieter is that it has one large fan as opposed to the two smaller fans found in earlier models. The last change is an aesthetic one on the design as the new 360 (S) has a slick new look with the uniquely positioned vents, a glossy black finish, and touch-sensitive controls (similar to the PS3). No more physical push-in buttons; a simple touch of the finger will do the trick to turn this console on.
Now for a quick match-up between the 360 (S) and the PS3 Slim on features:
360 (S) = 250 GB; PS3 Slim = 120 GB
360 (S) = Built-in WiFi 802.11 b/g/n; PS3 Slim = Built-in WiFi 802.11 b/g
360 (S) = Backward Compatible (Xbox Games); PS3 Slim = Not Backward Compatible (PS2 Games)
360 (S) = Plays DVD's (Attachable HD-DVD player accessory lost the HD war); PS3 Slim = Plays Blu-Ray's
360 (S) = 5 USB ports; PS3 Slim = 2 USB ports
360 (S) = No Web Browser; PS3 Slim = Free Web Browser
360 (S) = Gold Membership for XBox Live ($49.99/year); PS3 Slim = Free Online Gaming via Playstation Network
360 (S) = Streams Net Flix without disc; PS3 Slim = Disc needed to stream Net Flix
Note: Both consoles function at full 1080P High Definition.
With the specifications and technical match-up aside, I'm going to weigh in with my personal feelings between the two (as I own both). For the most part, this has less to do with a match-up between these two models in specific, and more to do with the two consoles in general. I have found that the Xbox 360's Xbox Live offers a better online interactive experience. The user interface is laid out a lot better, is easier to navigate, is more appealing, and has a great deal more content than the PS3's Playstation Network. The PS3 has an efficient yet boring user interface; It makes a great multimedia device with its walkman-style layout and Blu-Ray playing capabilities, but it lacks content and aesthetic appeal. Though games like Kill Zone 2, Heavy Rain, Metal Gear Solid 4, and the God of War series are among my favorite games, I find the exclusive offerings on Xbox 360 to be more desirable (Gears of War series, Fable II, Halo series, etc).
In the end If I had to prefer one over the other, the 360 would inch ahead of the PS3. However, it is not practical for me to only pick one system and forgo the benefits of exclusive games; I'm too much of a gamer nerd for that. That is why I bought both systems. This review is just for those people who can only have one, personally I think you've already shorted yourself if you love gaming and chose to only buy one or the other. I love the gaming experience on Xbox 360 better but I can't do without a Blu-Ray player or the exclusive gaming content provided through the PS3.
I love the 360 because of how much it improved upon the original Xbox and how entertaining the Xbox Live interface is. If I find myself being bored of the thought of turning on a console because of how dull it is to see the main screen display then that's pretty bad; and that's where the PS3 really turns me off. I'm hoping Sony will create a more appealing interface because the PS3 has so much to offer that tends to be overshadowed by the poor presentation. This is very unfortunate because when it comes electronics and entertainment (TV, movies, DVD players, Blu-Ray players, mp3/Walkmans, etc) I have been an unofficial spokesperson of everything Sony and there is no exception when it comes to the PS3; Sony makes quality products. In the prior generation, I loved my PS2 way more than I loved my XBox, but Microsoft really took online gaming, user interface, and general-online experience to the next level with the Xbox 360 and I found myself incredibly impressed. I also love the controller-style a lot more for the Xbox 360 (especially when it comes to shooter-games) due to the positioning of the analog joysticks and the fact that they are concave as opposed to the convex analog sticks on the PS3. For other people, the PS3's controller style may be more preferable (we are all different), but not me. I love my 360; everything from the games I play on it, to the Avatar I use to represent myself on Xbox Live. If you want to know which one I prefer, it's pretty clear its the Xbox 360. If you want to know which one to buy, buy both; anything less than a household with both consoles would be inadequate and, well... uncivilized.
Update On Jun 30, 2010: Update in regards to:
"360 (S) = Gold Membership for XBox Live ($49.99/year); PS3 Slim = Free Online Gaming via Playstation Network"
Sony has just released as of June 29th, 2010, the Playstation Plus Network. This is similar to Xbox Live as it will include features such as PS store discounts, auto-downloads, full-game trials, exclusive offers and early demos, free games and downloads and priority invitations on betas; this can be purchased for the annual subscription price of $49.99 -- same subscription price as Xbox Live.