Be sure you won't make a mistake with either of these two beauties.
They carry quite different an interpretation of this iconic model from Patek Philippe (i.e. the Chronograph Perpetual Calendar).
I won't choose yet but while the classical aspect of the 5970 faces the more contemporary and pure face of the 5270, the Lemania based movement and its legacy is facing the new very cleverly designed in-house CH 29-535.
Personally, I prefer the 5970's look (even if the 5270 is catching up) but I prefer the new movement.
It is a very exciting move you're about to make. Take your time and please keep us informed with many pictures!
Cheers Rahul, Mark