Neither. Keylight in Ae, Ultra or Primatte are the best choices. Keying in Pr is very very limited, especially if the screen has some flaws, like wrinkles or uneven lighting.
The only thing they are good for is making a garbage matte for the greenscreen before you use keylight or primatte. If you have to use premiere's color key then take a little at a time and use up to ten iterations if you have to. Maybe make to background white and do a trackmatte and put some blur on those edges.
Thanks for the info. I'll fire up after effects.
For my general info, of the three you listed, which do you consider "best"?
When you say Ultra do you mean Adobe Ultra?
I did mean Adobe Ultra or previously Serious Magic Ultra. I have no personal experience with Primatte, but have heard very positive reports. For relatively simple work with a good green/blue screen, which is properly lighted and not too much wrinkles, Ultra is easy, fast and effective, but it pays to have a look at the tutorials on how to setup a proper key. When you have rather bad lighting on the screen, Keylight is better and adds more flexibility, but is harder to master than Ultra. It also lacks the MSL (Master Set Libraries) capabilities of Ultra, but if you have never used Ultra before, you may be hard pressed to find any of the MSL's from the Serious Magic era around. Adobe has apparently stopped selling those, apart from the basic one which is included with Ultra. Maybe Karl Soule or Mark Mapes, previous Serious Magicians, can shed some light on the future of Ultra in the Adobe portfolio.
You'll also be very hard pressed to find Ultra anywhere if you are using CS4.
It is not included, cannot be purchased separately and there do not appear to be any plans to revive it.
The quote I was given when pursuing this after I purchased CS4, only to discover Ultra was missing, was, "...perhaps in CS5."
Since I have been using Ultra for such a long time when they were still Serious Magic and I have the CS3 version as well, I never noticed that Adobe took it off the shelves, but you are right. It is no longer available for purchase. Thanks for pointing this out. What a shame! Adobe again took over another company with a good product and managed to destroy it in a short time. Ultra, Audition,....