all topics are same in 1.4 & 1.5, but the 1.5 has next versions of topics.
e.g. understanding
soap 1.1 (in cert 1.4) will take same time as soap 1.2 (in cert 1.5),
same is with other topics e.g. BP-1.0 (in cert 1.4) BP-1.1 (in cert 1.5)
you would need to spend same time & effort for any of the version.
hope this will help you to decide which for version
you should go.
thanks.