Content to quality ratio-wise, I would say the PSN excels over XBL - Just look at the PS1 games library on offer, as well as fully fledged games such as Tekken 5 online and Warhawk. It's certainly a lot more interesting than the endless overpriced microrape crap that Microsoft keeps churning out week in, week out. I take the view of quality over quantity here. Paying a monthly fee just to go online and avoid the demo release delay that silver users are subjected to used to be tolerable for me, but now I think it's just dumb, especially when I've been playing PC games online for a long time now, and PS3 titles like Tekken and Warhawk also being without pricing restrictions. I have spent more hours on those two online than any equivalent 360 game (even Halo 3).
I used to be a massive advocate for Microsoft's plucky little console, but the way they just rested on their laurels and upped the ante on microtransactions with little improvement in the stream of contents quality while Sony are making huge strides, it has really ticked me off. Microsoft are being highly arrogant in saying they are the only ones with a real online service, and this attitude is what will make them third place in the end. It's a real shame really. The PS3's PSN service is making everyone open their eyes to how badly fobbed off 360 owners really are.
There's more updates as well, although you could take the view that those updates are only gradually implementing what Xbox 360 had from the start anyway.
That was my take on the online services for both - with regard to the actual games themselves, the 360 obviously comes out on top.