I have both, so I guess I can speak up. I see no reason to list the "pros", as they've been done to death already in this thread. Let's go with...
Disadvantages:
XBox Live - I'll be honest, aside from the price, I have trouble finding an issue with Live's service. I've never had lag problems, although I did have an issue right when I first started that ended up being caused by my router. Also, there was awhile ago about a year back where a few people had live connection issues. I personally didn't, but I'd heard that they were happening. We got a free game out of it, but it sucked. Still, I guess it was something.
I don't like having to buy a lump sum of "points" which I can then redeem for products, essentially putting a purchase price at the closest approximation of points, as opposed to a set value.
So... let's see... I guess I'd say that you get more of the youngun's bitching at you on Live, though I've heard it frequently in Home and on PSN as well. That could be due to the overall higher population, I'm really not sure. And of course there's the price. At about a buck a week, it's hard to claim that it's too high, but there is a price there, so I suppose that's something.
PSN - I've had trouble with lag and matchmaking intermittantly in a few different games, especially games that have just been released (I tend to pick stuff up pretty early, it's a rare game that I'm still playing online regularly 6 months after release).
LBP was the worst offender in that they completely took down their online component for around a week right after launch, and even afterwards I suffered frequent problems with lag. We're not even going to get into how bad MGO was when I tried it (Hint: Very).
I originally had myself running wirelessly, but I found that I got regularly disconnected from the PSN every few minutes. After seeing the recommendation in the MGS4 manual to switch to a wired connection, I decided to give it a try, and while it has assuaged the disconnect issue, I still got a fair amount of lag.
I don't like the way that PSN handles downloads, as well as how frequently won't allow certain things to be downloaded in the background. I absolutely loathe whatever horrible process they use to perform their updates. Updating my XBox to the NXE took under two minutes. Updating my PS3 has never ever taken less than 7. Also, the PS3 is frequently missing DLC, which means that games I purchase for that system may become incomplete as time passes.
I'm not too comfortable with the knowledge that Sony has placed the weight of the multiplayer component of their games entirely on the developers. This has less to do with the service and more my take on it, but as XBox owners often state, the system *is* Live. It's so built in to everything that we do with that system that it's hard to imagine a 360 existing without it. The PSN may be free, but it also feels... additional. Like an added gimmick, much like the web browser that's built into the system. Cute, but not really what the system is built for. By not building and supporting their own massive datacenter to house their online, putting it instead to the studios to provide their online support, Sony seems to have undervalued the weight of multiplayer in this generation of gaming.
So, for the TLDR version:
Cons of Live:
- Price
- MS Points
- Additional youngsters
Cons of PSN:
- Regular lag and matchmaking difficulty in freshly released titles
- Wireless connection is ill-advised (but available straight out of the box)
- Frequent downloads which cannot be pushed to background
- Long update times
- Incomplete DLC roster
- Network model not built with this generation's reliance on multiplayer in mind
- J