There are two computer departments.. Internal and External.. Internal is for maintenance of FBI network. External includes information technology specialist that do forensic work such as writing programs and investigating confiscated drives.. There's more to it, but that is the jist of it. Im on the forensics side.
Things to think about.
The FBI may not pay that much to start, but they are working very hard to make computer salaries more competitive in comparison to working at private companies. At current levels within 10 years you can be at the $80,000 range. If computer salaries go up like we expect.. you can expect more.
What room for advancement does the other company offer. You are not limited in the FBI and are even encouraged to continue schooling while you work.