Here are some informative size comparison slides from the official BMW X3 presentation. The first slide shows the new F23 X3 size compared to the outgoing E83 X3 and the second slide compares the sizes of the X3 to the X1 and X5. The all new X3 is not quite as much larger than the outgoing X3 as some have made it to be.
Slides courtesy of
Bimmerfile.