Why are consoles more difficult to develop for?

Hi, I'm just wondering why developers say it's more difficult to develop console games than PC games.

PS3: For the PS3 i slightly understand, developers say that the Cell Proccessor is hard to use, however it's exteremely powerful.

Valve had trouble and also Rockstar games, even with their years of experience they had trouble with Grand Theft Auto 4, so they had to delay the game until 2008. And Gabe Newell from Valve was said to of "TrashTalked" about the PS3, about how terrible it is, was this just a reaction of the difficulty of development or was it something else?

So why is it so difficult for them to use the PS3? Is the main Reason the Cell with it's SPUs, or having to becareful with it's 256Ram?

Xbox 360: The Xbox 360 had a headstart and has more graphical power than the PS3, and it's said to be easier to develop for the PS3. But how is it when it comes down to networking? I've never seen an Xbox game than can support more than 32 Players, but the PS3 reached 100+ With Mag, and DC Universe can possibly support 1000 players.

Also, would developing a Multiplayer game be even more difficult aswell?

Oh and one quick question, Publishers, Do developers only need a Publisher to get their game on shelves? such as EA? Including Indie Developers

And would that publisher be able to get your game on shelves and or digital download such as PSN and Xbox Live, and would you be able to update the game whenever you like and even run it on a Server if you made a MMO?

And Cross Platform Gaming? Would that be difficult? Valve did it with Portal 2 and another Company Created a game called Shadow Run for the Xbox 360.

Would there be restrictions, and could both platforms (PS3 and Xbox) play against eachother?

(Probably would be conflict between both Sony and Microsoft)

Thanks for reading.