Vinoth,
USB 3.0 has been added to the MC74 because the USB2 link was beginning to become the limiting factor in conducted testing when using maximum resources, this is unlikely to happen in the real world so most applications will not notice the fact that they have a USB 2.0 link over a 3.0 one, plus if you are transferring data at those speeds for any length of time you are going to need to have a serious data plan.
Regards
Matt