Currently it mainly depends on your future plans on short term.
Do you plan taking the OCPJP exam as well immediately after passing OCAJP exam? If yes, I would opt for the Java 7 version, because both exams are currently available and you already have an excellent study guide at your disposal. Currently the OCPJP8 beta exam is still not available (and thus also no study guides available). Otherwise you can take the Java 8 version. Remember you can't combine different version certifications.
There isn't much difference as far as OCA material goes - the main things seem to be lamdas, default methods and java.time API, so your K&B guide isn't going to waste.
Personally, I'm going for OCA 8. Java 7 may stay in production for a time, but no way it'll outlive java 8.
Krishna Srinivasan wrote:There is not much difference in terms of exam topics between 7 & 8. If you have some more time for the preparation, then prepare OCA 8 and write it. doing latest certification always good.
This is true for the OCA. There are a few extra topics on 8.
For the OCP, there are likely to be more differences. Based on the upgrade exam, we can inform Nashorn and much about functional programming is on the exam.
It's not clear to me whether you can take the OCA 7 and OCP 8. (And before anyone cites any statements from Oracle on this, it's not clear to me, because this seems like the type of thing they might change their mind on before the exam gets released.) I recommend taking both the OCA 7 and OCP 7 to match your study materials. You can still learn the Java 8 concepts independently. I recommend "Java SE 8 for the Really Impatient" for that.
Jeanne Boyarsky wrote:(And before anyone cites any statements from Oracle on this, it's not clear to me, because this seems like the type of thing they might change their mind on before the exam gets released.)
I was curious about this one myself, so I asked the OCP Team. Maybe I should/could ask them once every 3 months to anticipate any mind changes