Vesta:
-Discovered: March 29, 1807 by Heinrich Wilhelm Olbers of Germany (fourth asteroid discovered)
-Dimensions: About 578 by 560 by 458 kilometers (359 by 348 by 285 miles)
-Shape: Nearly spheroid, with a massive chunk out of the south pole
-Rotation: Once every 5 hours, 20 minutes
Ceres:
-Discovered: January 1,1801 by Giuseppe Piazzi of Italy (first asteroid/dwarf planet discovered)
-Size: 975 by 909 kilometers (606 by 565 miles)
-Shape: Spheroid
-Rotation: Once every 9 hours, 4.5 minutes
Below is an image to see a size comparison of how big the asteroids are in comparison.
Hope this helps!