Originally Posted by n is best

dear, so far as insp customs and p.0 are concerned, both are more or less identical. However, i would prefer insp customs over p.o because of its inspector tag. Mean to say when you are introducing yourself in front of someone, the word inspector looks more attractive and powerful than p.o .
Coming to the question's second part. I would prefer inspector customs over fia. Reason is simple, customs is a tension free and independent job with minimal risk chances. On the other hand, insp fia is less independent and officers are vulnerable to several threats. Moreover, financially insp customs is better than its fia counterpart. Promotions are deadly slow in both the departments.

so, keeping all these factors in mind, your order of preference should be:


1. Inspector customs
2. Inspector fia
3. Preventive officer.

Rest you can better decide once you make all the three. Best of luck for interview.