Agree. Like many have said on here and in many other places, it's easier to port from PS3 --> 360. But in order to do that, you must make you game run smoothly on the PS3 first, before your finished product can go to the 360. If you do it inversely, you can get it to run fine on the 360, but then run like shit on the PS3.
Contradictory to what patapon says, with 360 ---> PS3, THAT'S lazy, because it never comes out good. But with PS3 --> 360, developers take on the challenge, produce a quality product, THEN port to 360 which is an easier task. You could say lead on 360, then port to PS3 and that will present a challenge, and that won't mock Sony's moniker with the PS3. But remember, release dates are based on development cycles. I'd be much happier if the dev told me a game is releasing on a certain date (due to PS3 development) and that's the date I set, rather than them having to possibility of releasing an earlier 360 version, thus getting my hopes up for release. Only to be disappointed when the difficult PS3 port holds the game up