They are both similar, it really depends on the industry IMHO. Everything that I've worked on (Air Force's Research Lab's FDL3Di, NASA's BASS Code) is coded in FORTRAN. However, I've talked to people working in private industry that do a lot in C++.
Since so much legacy code is written in FORTRAN, I would recommend starting there. Once you have the understanding on one major programming language, adapting to another should be relatively easy.