One method (Sony's) funds the creation of unique content. This affords developers greater flexibility in design as the first party studio is not exclusively concerned with worldwide software sales when organizing their first party lineup and should the initial offering be lackluster in sales but a good game they'll likely get a second bite at the apple.
The other method (Microsoft's) pays to lock already in-progress work to a single platform, bringing zero new or creative elements to the project. It also fails to offer any assurances of continued support for the developers should sales disappoint since MS has no real investment other than a lump sum check of sunk money, and therefore can easily walk away (which they have, a bunch, though they've done that with first parties too).
If MS was just focused on picking up smaller independent studios who lack the means to self-promote or self-publish then that is something else entirely. But when they go to companies like Crytek and Platinum Games (major multi-studio developer who has ample distribution avenues open to them), or even EA and Capcom (major 3rd party publishers with the means to fund and distribute pretty much any title anywhere themselves) it's shearing the sheep a bit close for comfort. They aren't allowing any new content to come to the market, they're just locking previously in-progress content into their walled garden.
It's a shame because once upon a time Microsoft actually had some pretty capable people overseeing their entertainment software. But with the Xbox that was all cast aside and instead they focused on trying to figure out what content would have market relevance but was still purchasable late in life. That's where Halo, Gears, etc. all came from. Not from Microsoft cultivating a family of first party studios that make great software on their own.
