How important is the difference between ECDHE_RSA and DHE_RSA security-wise? edit: I asked because Opera showed a site's free StartCom certificate as "TLS v1.0

How important is the difference between ECDHE_RSA and DHE_RSA security-wise? edit: I asked because Opera showed a site's free StartCom certificate as "TLS v1.0 256 bit AES (1024 bit DHE_RSA/SHA)". I checked with Chromium and there it is shown as ECDHE_RSA though. This is confusing...