I personally think its better to take the exam before the changes apply. One, you won't see any surprises such as the new integrated reasoning section. Two, there really aren't many books published just yet that cover the integrated reasoning section. That being said, OG 13
is coming out in April. This book is likely to cover this new added section.
As far as scoring is concerned, your quant and verbal section will not be scored any differently. However, with the new format, instead of having to write two essays in the AWA section, you'll only have to write one essay plus answer a few integrated reasoning questions. Hope that helps