I did not realize the prices to acquire 5070P and 5970J were almost the same. The easy answer regarding which to purchase at about the same price is the 5970J with the greater complicatons. But the more subtle answer may not be as easy.
My sense of the 5070P is that with PT case and blue dial on top of such an already beautiful reference, this watch is and will remain a super-star. More than simply hype, this is perhaps the most beautiful pure chrono ever produced, and it is hard to imagine that future manual wind chronos from Patek or anyone else will supplant it. The 5070P in my book is by far the most desirable of the 5070 series.
The 5970J is a beautiful, almost vintage appearing chrono/perpetual, hyped in its own right, and rightfully so. But for me the G, R, and probably P would be more deisrable in this reference.
Don't get me wrong, I love manual wind watches, including perpetual calendars, but I have also come to realize that there is a lot of satisfaction in simple watches, including a "simple" chrono, without the occasional frustration of resetting a perpetual calendar. More complicated does not necessarily mean more desirable. So my preference between these two watches for my own collection would be 5070P. No doubt there is also some "investment" consideration in deciding between these watches at the same price--perhaps though not much of a determining factor for the long run since both will likely do well.