Probably not, but bandwidth isn't the only measure of a link. There is also an issue with clock rate, and how this effects the latency across the link. Now, realistically, I doubt the time it takes to clock the packet out onto the wire (the serialization delay is what this is called) is really that much different here, but it could have some impact. Note that the serialization delay depends on the clocking, not the bandwidth.
So, a 2mb link with a full 2mb bandwidth will clock the same as a 2MB link with a 513K committed access rate, if that helps to understand how this workd better.
Russ