There are several points to take into account when comparing both systems. You can't solve the PlayStation vs Xbox debate simply based on the graphics or value of each console. In this article, I will be comparing both systems with facts while keeping a completely unbiased approach.
The PlayStation 3 is currently about 100$ more expensive than the Xbox 360. The 80GB version is sold for 399$ and the 160GB for 499$ while the Xbox's 60GB version is sold for 299$ and 399$ for the 120GB's one. 100$ is quite a big difference but you will see that it's not that bad after reading the other points.
Luckily, the Xbox 360 is pretty cheap because it has an extremely high failure rate. Some say it's around 16% but retailers are reporting much higher numbers going up to 33%. The most famous problem is the always annoying Red Ring of Death (RROD). There is literally thousands of programs being sold on the internet that are supposed to teach you how to fix it yourself but it remains a very serious issue. The PS3, on the other hand, has an amazingly low defect rate which is reported to be around 0.2%.
This is probably the only point that can't be argued. The PlayStation has built-in Wi-Fi, Blu-Ray and Bluetooth makes it very customizable with third party devices, the 360 has none of these. You can get the 60GB version and just install a 300GB laptop drive on your PS3 if you need the extra space. You can store and stream media, the Xbox can do the same, except the storing part.
Apparently, the PS3 has better graphics but it's not always the case. The Xbox 360's GPU is actually more powerful than the Cell processor of the PlayStation.
This used to be the Xbox's strongest advantage. Since it came out before the PS3, it obviously had a wider choice of game but things changed. In 2008 alone, the quality of the new titles was pretty even for both consoles and I'd say that in 2009, so far, the PlayStation is leading with games like Killzone 2 and inFamous coming out soon. The 360 still has very good exclusives such as the Halo and Gears of War series.
This is where I would give the Xbox extra points. Xbox Live subscription fee is about 50$ a year while PlayStation Networkis free but, unfortunately, you get what you pay for. XBL has many advantages and is a lot more popular than its counterpart. One thing that makes XBL stands out is the gamerscore, it's human nature to always want to be the best, accumulating points through in game achievements is a really good idea that Microsoft came up with.
Overall, I think that both consoles can be very entertaining, the failure rate of the 360 is a big problem but it's still cheaper than the PlayStation 3 and you could be lucky and never have any problem. The PS3 is very reliable and technically impressive but your online gaming experience might feel incomplete. The two systems are so good that my advice would be to choose your games first. Find a few games that you really think that you would enjoy and just get the console that comes with it!