A few days ago I received a question from the contact page of my OracleCertificationPrep website. An Oracle professional had recently earned his Oracle PL/SQL Developer Certified Associate certification and wanted advice about the next step to take. In particular, he asked whether it made more sense to pursue the "1Z0-141: Oracle Forms: Build Internet Applications" exam to become an Oracle Forms Developer Certified Professional or to study for the "1Z0-146: Oracle 11g Advanced PL/SQL" exam in order to become an Oracle Advanced PL/SQL Developer Certified Professional. He did not mention the third option which is to take the exam “Oracle Fusion Middleware 11g: Build Applications with Oracle Forms” to become an Oracle Certified Professional, Oracle Fusion Middleware 11g Forms Developer. Oracle Education recently scheduled 1Z0-141 to be retired (and then issued a temporary retrieve). For this reason, choosing 1Z0-151 might be the better option for professionals with a goal of becoming a Forms developer.
Both of the Forms certifications are for individuals who will be doing primarily client-based PL/SQL supporting Forms applications. The Advanced PL/SQL certification is for individuals who will be doing primarily server-based PL/SQL development. I cannot get deep into all of the differences between the two without turning this post into a novel. However, I’ll note that Forms PL/SQL development will be within the confines of the development environment and tends to be small blocks to provide specific functionality to a given page. Server-side PL/SQL is often (although not always) considerably larger blocks. These are normally stored in packages and perform a wide range of functionality.
The actual question asked (and one I see a great deal on the OTN certification forums) was “Which certification is best?” (hence my post title). Unfortunately, that is a question without an answer. If one certification was the best option in every case, then all other certifications would be irrelevant. What he really meant by the question was "Which certification is most likely to get me hired?" Now that question there is an answer to. Unfortunately I do not know it. He is in India (although he did not indicate which part). I do not keep track of the job market in India, but common sense says that the job market is not the same in all parts of the country. One city might have a need for Forms developers while another might need server-side PL/SQL developers.
The best way to find out is to do some research on job openings in the desired area – preferably over a period of several months. Unfortunately, it is sometimes hard to tell what type of PL/SQL developer a company is seeking. This is largely because the Human Resources people writing job descriptions don't understand the difference. If the job description for a PL/SQL developer mentions Forms or Oracle Fusion, you can be reasonably sure that the position is for a Forms developer. If it doesn't, then the position is probably for a server-side developer. That said, you can start as either a client-side or server-side PL/SQL developer and move to the other at a later date. The hardest task for professionals just starting out is getting their first position working with Oracle.
For candidates who already have jobs and who are developing in server-side or client-side PL/SQL (and have no desire to change), choosing between the exams is much easier. Many years ago, I did some Forms development, but the vast majority of my development experience (and my interest) is in server-side PL/SQL. When I pursued my OCP in the development track, my intent was to improve my programming skills in server-side PL/SQL. With that as a goal, the Advanced PL/SQL certification was obviously the better choice. I may take 1Z0-141 or 1Z0-151 at some point in the future simply to continue expanding my skills. However, the more relevant exam for gaining my OCP was obviously 1Z0-146.
If you have no personal or job-market related reasons for choosing one over the other, my own suggestion would be to go for the Advanced PL/SQL Developer. Some of that is certainly bias on my part, but it also seems to me that Oracle Forms is on a down slope in usage. I don't think that it will go away entirely for quite some time – certainly not in the next five years and probably not in the next ten. However, I suspect that its usage will steadily decline. By contrast, neither Oracle nor server-side PL/SQL is likely to decline in use any time in the foreseeable future. Whichever option you decide to pursue, good luck on the exam.