Hi Kiranmayi,
From few years of following PGSM admission and almost making into there..

..some things that we can see are:
1.) The admission is highly profile based - meaning once you get a decent CAT score (say 90%ile and above), they look at individual profile, amount of work experience in IT etc before giving out the call. There is no fixed cutoff as such since they accept CAT/PGSM Admission test score and even GMAT. So they do some kind of normalizing these scores and finally send out calls based on this score + profile of the candidate
2.) With two years you are just about eligible for PGSM. There are normally only a handful with 2 yrs work exp. But this shouldnt discourage you from applying. Perhaps your CAT score and may be kind of work you do and acads etc might be good that they can take you in. Normally I notice that ppl with abt 4 yrs work exp have the best chance of getting a call for interviews.
3.) There are no advantages as such bet the exams since in the end they normalize scores. But best adive would be to try CAT first and if your score is not good, you have option of sitting for the PGSM test. I you face CAT once you have seen it all! :)
I would advice you give a shot at it.
regards,
Praveen