The key difference being that the PS4's raw performance advantage is available at all times, on all types of processes, regardless of internet speeds or the lack of a stable connection. Cloud based computing would be very nifty in some select instances or with some types of games, but it would be a method with more variables and a much narrower array of potential uses.
It would also be an extra development step for multi-player games.
My guess is that most developers aren't going to use it very much, outside of XO exclusives, just as most developers aren't going to attempt to squeeze more from the PS4's extra horsepower. It's just a lot easier to make multi-platform games essentially the same.
That being said, it will be interesting to see which console ends up with the more advanced exclusives.
