Just thought I'd throw in my 2 cents...
My favorite feature of the xbox is the dolby digital. If you've got a home theatre system, there are many games with dolby support, and since xbox offers on the fly encoding, the games end up sounding very nice indeed.
I was confronted with this problem back in Feb. when I bought my xbox. I'd been waiting for the xbox since Early 2001, so I eventually ended up going with it. Not having to buy memory cards is very nice, and I dunno why, but the xbox just appeals to me more (biased opinion cause I don't have a ps2? ). The only way to decide which one to buy, really, is to carefully look at what each has to offer, hardware and software. Look at the games out now, and the games coming out, and see what you'd be interested in. Take a look at the possibility of their online gaming network, that might be of interest as well. How much is the broadband adapter for the ps2 anyways?
Most of that applies to gamecube as well, which I've been more interested in as of late...