It's hard to compare the Mac's G4, and the Athlon and Pentuim on the other side. G4 uses a RISC architecture, while the Athlon and Pentium use a CISC architecture... Both architectures have their advantages and disadvantages.

Personally, I would favor the Athlon as the best buy for the $. Mac is an alternative only if the software you want to use is available for the Mac...