Hi,
As far as I'm qualified to answer, if I had to choose an everyday watch (what I'd love a 5970 to be for myself) I'd keep the 5970.
I love that watch. It looks like a great companion.
If you're looking for the extreme Patek chronograph, go for the 5004, but be prepared to sell it for a 5959! 
Have you imagined a 5950 PC!
Cheers
dje