that depends upon multiple factors like time/deadline you have and other things. keep in mind that they both are different exams. As you might be already aware one is associate certification and the other is programmer certification. the latter covers much more objectives than the first. also you may consider to give OCPJP 7 exam. the prerequisite of this exam is OCAJ 7 or if you are following upgrade path then any scjp/ocpjp certification. so in both cases you can achieve ocpjp 7. but both techniques/paths have their pros and cons. i recommend you search this forum since these questions are very frequently asked here.
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com