I personally prefer the bigger handles the Xbox 360 controller has. When I had just bought my PS3, the controller felt really odd at first - the Xbox 360 controller was the only controller I had used in a long time, and in comparison the PS3 controller felt way too small at first.
I quickly got used to using it, and meanwhile I think the PS3 controller is superior in pretty much every respect - but I would still prefer if the handles were a little longer.