Here is an interesting article from DSP DesignLine that explain how to choose between the two devices.
DSPs and FPGAs both offer advantages for signal processing. Here are the design guidelines you need to choose between DSPs, FPGAs, or a combination of the two. Topics covered include device cost, performance, NRE, and availability of application-specific features.
By Bamdad Afra and Amit Kapadiya, Nuvation
(read article)
