1 reason for the delay to semptember:

to compete with Halo 3.

You're telling me they want to get crushed? Or are you joking?

Also, I don't think it's a good idea to launch two important PS3 games at the same time... They'll likely steal each other's sales.

If getting "crushed" would be a bad business decision, you could also ask why they wouldn't just want to delay it for another month.  I mean they already have heavenly sword and Ratchet&clank for september. 

But, even though I really doubt that these games will steal the 360's thunder in sept, I still think that whatever they can throw against halo3 for september will keep sony from having a horrible month.  These kinds of matchups happen all the time, thats why Sony paired up Resistance against gears, even though they knew that they would be beaten in the market place, but it doesn't matter, you have to do something and do it as good as you can and you shouldn't be scared of the competition.  Neither company should be afraid to go head to head with any of the others if they want to get anywhere.