I prefer PSN because its free and is the same as live. You get 16 player cross game text chat on the PS3 and with a keyboard hooked up(you can get a USB keyboard for $10) you can chat with 15 people in ANY game, even MW2 which you can't on xbox 360.
Communication is communication. Text chat is actually awesome on the PS3 because very few people have mics, this way we can communicate with everyone. Its also easy to use as well, but not as easy as voice chat in the 360. But at least you don't get kicked out of your chat room.
And another awesome feature is you can have three rooms simultaneously. All cross game, I believe.
PSN also offers much more freedom than XBL because of which games like LBP are possible, because of which UT 3 has mods on the PS3, because of which Portal 2 is the best on the consoles on the PS3, because of which Oddworld is NOT on the 360(exceeds 2 GB limit).
I mean, $50 60 and we don't even get cross game text chat for people who don't prefer voice chat.
About the speeds: They are the same. Only while downloading certain updates for some games have I felt the speeds a little slow. Demos and stuff download very quickly on the PSN.
The integration of marketplace in XBL: That's a convenient feature on the 360, that's true. How many times do you purchase something anyway? Its there on many PS3 games as well though, but it makes you quit the game unfortunately, unlike Xbox 360.
Everything on XBL costs money. Everything, including avatars, themes, and even some videos. The only things that are free are demos and some videos. And trailers of course.
On PSN you don't have to pay for at least 100s of themes, wallpapers are also given for free, and GUESS what? You can make your own theme as well. The only themes that cost money are premium and dynamic themes, and as far as I can tell Dynamic themes are totally worth it. Flash themes are greater than any theme on the 360.
All this for free. That's right folks.
Then there's Playstation Home, which has improved dramatically since I last visited it. Its at least 10x better than game room when I used game room, because game room didn't even load for me.
Then there's PS plus for anyone who's interested. I don't have it but that's because I am not interested. You can get dynamic themes for free if you have PS plus, avatars for free, some PS one games, and every once in a while a huge update always comes through. Like for eu PSers there was fallout DLCs all for free but for one week. The US one's got MAG for free along with some others which I don't remember.
Without PS plus, I consider PSN to be a superior service than XB live. With PS plus, it definitely is.
