If you mean you're planning to resit next year, I don't see the reason why it'll be better to sit the new spec. I believe next year will be the final year for A2 resits for the old spec and seeing as your problem is your A2 modules are low, why don't you just resit the A2 modules next year?
You won't have to relearn anything that's new in the new spec and you'll already know most of the content in the old spec. So all you need to do is make sure you revise for the modules so you can do well next year.