Hi Tim, Aman and OP
In my opinion, if somebody wants to do a good career in Oracle, he should firstly give 9i certification. As sir Hans Forbrich said in one of certification topics in OTN - I forgot what Mr. Hans said exactly (I'll try to find out his post), but the main sense was that he gives superiority to person who is 9iOCP and not 10gOCP, than who's 10g OCP and not 9i OCP
Firstly, I was thinking that I should have 10gOCP. 9i now has been retired, even though its using by many companies. Then, by investigating a little (and being 10g OCP), I've found out that being 9i OCP is a very good option, is superiority and will impact to career.
Thus, I started prepare to 9i exams and have passed 3 of them
I think that the main difference between 9i OCP and 10g OCP is in Performance Tuning. There's additional exam in Performance Tuning in 9i, but in 10g all performance tuning actions are automated by using Enterprise Manager
I'd be very glad to get your opinions