Sony recently came out with a chart that attempts to illustrate that, in spite of its apparent higher price tag, the PS3 is a better value than the 360 or the Wii.  Their comparison to the Wii is a bit weak, but they have a very good point on the 360.  One of the most glaring issues with the 360 is that WiFi is an add on and it costs $100. 

Now, first of all, $100 for what's really just a WiFi adapter is insane.  I can get a WiFi adapter for an older laptop that doesn't have it integrated for under $20.  But even in making that statement notice that I said, "older".  The reality is that modern laptops have WiFi built in because people use it all the time and because it's dirt cheap to have WiFi integrated onto a motherboard.  

So it's worth making the point that Microsoft made a deliberate choice to not include WiFi.  Arguably, by making it an add on, they probably made the main system hardware more expensive because it had to provide a way to modularly plug that feature in.  Where as including WiFi integrated onto the board would have cost them nearly nothing.  By making it an add on that almost everybody was going to end up buying for $100 though, they were able to raise the effective price of the console while still keeping the advertised price point lower. 

It seems to me that, in the long run Microsoft went with a plan that's better for their bottom line and Sony went with a plan that's better for the average consumer.  Granted, you can get a 360 and play games without getting a hard drive or WiFi, but odds are you aren't.  You'll either get the higher priced all inclusive model, or you'll end up buying the add ons eventually.  Then, on top of that, you'll pay $50/year for the privilege of playing games on a network using your $100 WiFi card.