Do noted why DSTA offer higher paid. Some projects can only be done by Singaporeans, hence the limited pool of workers they can draw on force them to paid high. A number of skills you learned are not transferable should your decide to move to private sector. DSTA will not blacklist you. They want to get as many Singaporean engineers as possible and can't be picky. My classmate got in with only a pass degree from NTU engineering.