@Agafaster : around 1x more up to 10x for the 1.0GHz CPU module depending of what you're doing with it ...
ta.
I know basically there will be either a mathematical difference, or a quantum leap given the G3 not having the G4's altivec unit, but as a rule of thumb, I used blade-enc to encode Master Of Puppets (track) to MP3, it took about 3-4 mins (rule of thumb).
The things I use my A1 for are Web, MP3 coding, and E-UAE emulation.(and coding, but I hardly get time these days !)