PS3 longevity compared to 360 is better. Even though 360 came out before, look how quick it dies. PS2 is still outselling 360 even with the massive people on 360. PS2 has been out since 2001, competed against Dreamcast, GameCube, and regular XBOX. Which one of those systems are still being made, or have new games coming out on them? None except the PS2. PS3 was made to last longer with proper care, so PS3 is really an investment, seeings how you spend more money with Microsoft's 360 with online, equipment, games, etc. PS3 in the long run is cheaper to keep than 360, and has less failure rates/problems than 360. If you want to get a 360 you might as well get a Wii. Sony stated it might not make anymore game systems after 3 (I think its a lie), obviously Microsoft is working on a next gen console already because they need something better than 360 to compete with Sony technology via gaming. So think about what will last longer and cost cheaper in about year or 2 when you consider game systems.
PS3 is like a computer, you can change the HDD with almost any 2.5in HDD up to 500GB (laptop HDD). 360 you can only go up to 120GB with its own special HDD. PS3 you can install a OS and use it as PC (Other system which can be Ubunta, Linux, Yellow Dog, etc.), they use this on basic laptops which uses basic codes so you can access files and load stuff (really complicated but fun to play emulated games on through PS3, adds to stuff you can do on system). You can choose how much space for OS & gameing, you can use external HDD, & flash drives to save, & copy music, videos, & pics through PS3; you can't do this with 360. PS3 is wireless (built in), or can be used with broadband for internet access. 360 has to be plugged in through broadband, or use wireless by buying adapter for $100 plus tax. PS3 has free online service with system for gaming, 360 has monthly plans for internet access with system which will eventually hurt your wallet and make you cut back on other necessities you may need. PS3 also has a built in Blue ray disc player, those run up to $600 for one of those, it comes built in to a PS3 (more bang for your buck). 360 is trying to get a hold of a way to make a add on so 360 can use blue ray technology/drive on system, since HD DVD failed miserably to blue ray (add on for HD DVD player drive was around $100). So in all, make your own desicion if you want, but I had to compare systems and give some history and future of the games, I guess you can call me a game head or some **** like that.
EDIT: PS2 is not 10 yrs old, I guess the guy under me had a typo, but PS2 was released in America October 26, 2000, originally in Japan March 4, 2000. So the system is coming up to 9yrs in America this October. 360 came out November 22, 2005 which would make the system coming up on its 4th yr. this coming up November.