I have both consoles (I have the 80GB Korean PS3). I'd support your choice to go with the PS3. That's not to say that the 360 is not a good system, with some cracking games available for it.
But here are the reasons:
1. Hardware. The 360 is simply unreliable. Moreover, the PS3 is technically superior.
2. Noise. The 360 is very loud, which makes it useless as a media centre. The PS3 is pretty quiet, such that I don't notice it when I am playing Brian Eno's Apollo album (which is a really quiet album of ambient music).
3. Features. The PS3 simply has more features, like Bluetooth built in, the ability to run Linux on it, and so on. It really feels like an all in one entertainment centre, whereas the 360 feels like a console with the other stuff bolted on as an afterthought.
4. Interface. The XMB is much better than the 360's Blade interface. It's simpler and nicer to look at. It enables access to far more options than the 360 has, and does so much more simply (trying to change network options can be a pain on the 360). The new XBox Live blade doesn't match the other blades, which is inconsistent.
5. Polish. When the PS3 boots up, you get the wonderful sound of an orchestra. It really is classy, and sets the tone for the user experience. Everything in the user interface is so clean and nice looking that it shames the 360. Someone really cared about the user experience. The XMB is probably the nicest looking interface I have seen that is not designed by Apple. You can see this clearly in the music visualisers. The PS3's is fluid and clean, like a great piece of electronic music. The 360s is like having a bad acid trip at a Bulgarian circus.
6. Online. PSN is free. PS Home will make it better than XBox Live. What all online console services have lacked so far is a proper feeling of community. It appears that PS Home will provide that central sense of community (like that an MMORPG has). With a central meeting place, it will be much easier to make friends than trash talking in a game lobby.
7. Blu Ray. It's going to win. Moreover, since MS has stated that all 360 games will come on standard DVDs, this will cripple the 360 as the consoles age. You can simply fit a whole lot more game on a Blu Ray disc. If you like gigantic games with mega huge environments and tons of graphics, the PS3 will have them, and the 360 won't.
8. Dominance. Microsoft took a gamble in releasing the 360 early. While it is not a forgone conclusion, that gamble appears not to have paid off. The PS3 has tracked the 360's sales since launch IIRC (i.e. if you put them at an equal starting point, its about the same so far). That's all that Sony has to do, because it has the superior machine. As time passes, the value of the 360 in comparison with the PS3 declines. Nintendo is the dark horse, but the Wii isn't an HD machine.
Don't get me wrong. I still like my 360, but the PS3 is just a lot better. There has been so much anti-Sony sentiment in the English media that it has given the appearance that the PS3 is in trouble (and there's a small amount of racist sentiment in that). It's not.
Even Paul Thurrott liked the PS3. That should tell you something.