What is the difference between ECDHE-RSA and DHE-RSA?

I know that DHE-RSA is (in one sentence) Diffie Hellman signed using RSA keys. Where DH is used for forward secrecy and RSA guards against MITM, but where do the elliptic curves in ECDHE-RSA are exactly used? What upsides has ECDHE-RSA over DHE-RSA?

ECDHE suites use elliptic curve diffie-hellman key exchange, where DHE suites use normal diffie-hellman. This exchange is signed with RSA, in the same way in both cases.

The main advantage of ECDHE is that it is significantly faster than DHE. This blog article talks a bit about the performance of ECDHE vs. DHE in the context of SSL.
