Many motherboards were not compatible with those cards due to voltage issues with the card's requirements from the AGP slot. Another advantage that PCI cards have over AGP cards is cost. Inherently, PCI cards cost less than AGP cards. The performance advantage of AGP is supposed to be such that buying the card gives the user a large enough performance advantage that it can justify the higher cost of the AGP card. Ok, enough of the text and details.
Lets get to the meat of the information.
All cards and chips were clocked at their standard speeds. Both cards come with a default clock speed of 166MHz for both memory and core clock speed. As you can see here, there just is not a lot of difference between the two cards. Let's see if the difference between the two is noticeable in Falcon 4.0. Well, if you can notice a framerate difference of about .005 FPS, then getting AGP might be something you are interested in.