I'd say, despite my usual thought that the latest is probably the best, that you should take whichever you feel more comfortable with. If you use 1.4 in your professional/academic life and know that one better, take the 1.4 exam. Otherwise, prepare for the 5.0 exam.
Theodore Jonathan Casser
SCJP/SCSNI/SCBCD/SCWCD/SCDJWS/SCMAD/SCEA/MCTS/MCPD... and so many more letters than you can shake a stick at!