This week's book giveaways are in the Refactoring and Agile forums. We're giving away four copies each of Re-engineering Legacy Software and Docker in Action and have the authors on-line! See this thread and this one for details.
If you are prepared for the 1.5 exam, then by all means take the 1.5 exam.
On the other hand, if you are prepared for the 1.4 exam but not the 1.5 exam, then my opinion (and you will certainly find others if you search this forum) is that you should go ahead and take the 1.4 exam in order to get certified and move on.
"We're kind of on the level of crossword puzzle writers... And no one ever goes to them and gives them an award." ~Joe Strummer sscce.org