Hi, Dennis -
You are probably looking at the G4 (Digital Audio) 733MHz and the QuickSilver (01 - the first series of the QS models) 733MHz models - those are the only models which have the same processor speeds between QS and pre-QS models.
There are some differences -
The G4 (DA) 733MHz was the top-of-the-line model for its series, and the QS 733MHz was the bottom-of-the-line model for its series.
L3 Cache -
G4 (DA) 733MHz - 1MB
QS 733MHz - none
Power Supply -
G4 (DA) 733MHz - 338W
QS 733MHz - 360W
Minimum OS -
G4 (DA) 733MHz - Model-specific OS 9.1.1
QS 733MHz - Model-specific OS 9.2
either can use a retail OS 9.2.1 Install CD
Other than the above and the graphics cards, for which there are too many choices for each to list, the machines' specs were much the same.