If you are referring to an AMD Phenom 9500 (which is not an Athlon)...
Compared to an Intel Core 2 Quad, no. In most regards, AMD Phenom chips are not as fast nor as efficient when compared to a Core 2 Quad. The first Phenom 9500 and 9600 steppings even had a design defect that could cause system instability under extreme circumstances.
Compared core-for-core to the previous AMD K8 (Athlon) architecture, however, the Phenom is definitely a better choice, especially if the software you want to run typically uses more than 2 CPU cores.