I would personally take the latest certification porssible i.e. SCJP 1.6 which as far as I know has very little difference to SCJP1.5. Is there a particular need for you to do SCJP1.4 or SCJP1.5 why not do SCJP1.6?
well, it also depends upon the time interval in which you want the certificate in your hand because knowing the internals of java 1.5 may take sometime not of a kind of 1-2 weeks.
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