Hubble question

I was recently reading an article on the future Hubble updates in
Science News and I was a little confused. The article covers a number
of subjects including the new Cosmic Origins Spectrograph and the
older STIS (Space Telescope Imaging Spectrograph).

"Another new device the crew will install is the Cosmic Origins
Spectrograph, or COS, which will separate ultraviolet light into its
components. The spectra will provide new information on..."

But then later we read

"Installed in 1997, STIS separates ultraviolet light into its
component wavlengths to reveal the..."

Anyways, it is clear from the stuff after the elipses that these two
devices ultimately perform different functions. But how are they
really different? I mean how much difference can there be between two
devices that separate ultraviolet light into its component
wavelengths. Is the new one simply more sophisticated?

Matt