With regards to the policy of MS on late ports to their system... do you suppose they would just allow it, with no additional content?
Extra content is standard practice for late ports. The content can often merely include DLC from earlier versions, as I recall, if its sufficient -- (eg: Oblivion).
This has nothing to do with Sony's business policies, other than they are unwilling to fund development of projects they aren't actually publishing themselves, unlike MS, in return for timed exclusivity, apparently.
EDIT: Didn't Sony announce an across-the-board help-your-bottom-line deal for making exclusive PSN titles recently? The difference here being that Sony is helping small self-published titles see the light of day (i.e. giving gamers something fresh and new, that they wouldn't see otherwise, in return for exclusivity -- they even let the devs retain the IP), whereas MS is buying timed exclusivity for major titles (i.e. keeping people who don't own a 360 from having a game until the benefits of exclusivity have mostly warn off for MS).