I recently picked up an older DUPLO elephant from the flea market for my intern, and decided to do a comparison with a modern version she also owns. As you can see, the original DUPLO elephant has more of an old-school LEGO feel to him, while the brand new elephant is much smoother in design. The new version, while slick, lacks the LEGO styling cues of the original, and looks like he could be part of any modern kiddie toy line.
Additionally, the older DUPLO elephant's head rotates up and down. His nose is designed to grip, well, anything a DUPLO figure can grip, but it also has the added bonus of the ability to rotate 360 degrees.
The new DUPLO elephant looks fun and cartoony, and his pose is less static than his elder cousin, but without the pegs on his back you might not even guess he's DUPLO. He does have tusks and a circus themed blanket painted on his side, but his head doesn't move and while his nose will hold objects just the same as his older counterpart, it doesn't rotate at all.
The newer elephant does have four pegs on his back, however, while the older version only has one. So larger items can be pegged to his back, while the older elephant really only holds a single figure. You can also really see the seam on the old elephant where the two halves come together.
Bot elephants are a lot of fun for my intern, but from a design and aesthetic perspective, I prefer the older one. He looks and feels much more like a LEGO animal, and he can even be used alongside LEGO minifigures and not seem out-of-place (if a bit large, even for an elephant.)