While Sony insists that the PlayStation 3 packs more horsepower than the Xbox 360 there have yet to be many games that show the PS3 with a definite edge. In an interview with GamesIndustry.biz the head of Sega Racing Studio says that it's the PS3's development issues that keep PS3 games at 360-level:

How have you found development on the two next-gen console platforms relative to one another? Obviously it's quite a contentious issue.

Yeah. For me it's always been Pretty much the same. Sony always create very technically innovative hardware and always have. PlayStation 3 is no different in that respect. The flipside of very innovative hardware is that it takes you a while to get up to speed with it. The learning curve is steeper in that you have to get into it and understand exactly what the benefits are, and understand exactly how to do certain things to get the most out of the platform.

With Xbox 360 obviously development is simpler. The development tools and support you have are obviously excellent. So that really is the trade-off. We're very happy - the game looks identical on both platforms; the feature-set is exactly the same. We've sat them side by side and you're really hard-pushed to tell the difference. I think that's a testament to where you are with both platforms. The learning curve with PlayStation 3 is steeper, but once you're there the opportunities are very exciting.