In general, it is advisable to go for the most recent certification. But OCPJP 7 is not even in beta yet. It could take anywhere from 3 to 6 months for it to go live. If you have time now, take OCPJP 6 now otherwise take OCPJP7 later.
Also, for OCPJP 7, it seems Oracle has split it into two (details are still hazy). So if money is a consideration, you can take OCPJP 6 now.
Hi Yadu, besides all comments about differences between SCJP 6 and 7, you should consider trying SCJP 6 also for a professional reason. Upgrading JDK on stable projects can be very tough so it's unlikely that the company where you work or would like to work are already using Java 7. It will take much more time to companies adopt Java 7 than Oracle to launch SCJP 7.
I've been trying to keep up with some of the interesting changes in the OCPJP and OCAJP certifications. One of the really interesting changes is the fact that to get Java 7 certified as a 'professional', you need to pass that OCAJP certification first. It's a two step process, which also means dishing out money twice for sitting the exam.
Should i wait for OCPJP & or give OCPJP 6 now???
If that is specifically the question, I think I'd recommend doing OCPJP 6, if only because the process is streamlined, you only have one exam to pass in order to obtain your designation, and because writing one exam is cheaper than writing two. So, study your behind off for the version 6 exam. Then, if you really are hungry for the Java7 certification, just take the Java 7 upgrade exam.
To figure out what's new as far as the exam goes, it's best to go to the objectives for the Java 7 Professional Certification Upgrade Exam. That lists out quite nicely what is new. So, for the most part, you need to study pretty much everything that was on the old exams, so any Java 6 certification resource will do, and then spend some time researching these new topics.
My buddy Sal and I have been writing up some content, one exam objective at a time over on TSS, hoping to help people focus on what's important with the new exam. I've got a ways to go, but here's some of the content.
Okay, I can see that this is getting out of control. A little too much self promotion. I've created a page in "Blatant Advertising" to update some of the OCPJP content that's being created. Much of it is crosslinked to pages at JavaRanch, of course.