Dear CL,
You can get a 5970 later, any time any metal.. 5004 is 8 times rarer than 5970. (basing on % of sighting). In 2004, I have tried one 5004 on and the 36mm size is a forever classic. Even my wife could wear it. It was a 5004G with a 3970 dial. At that time I found it unappealing (and my wife was next to me..) so I passed it on. I have been regreting it everyday, man!
BTW, what is special about Patek watches? It's fine polishing and the breath-taking skills in getting so many complications into one watch.
The 5004 is the acme. Perpetual calendar + a split seconds chronograph. When the big watch trend is gone, 5970 will look awkward and by then, you will never get a 5004.
GET IT WHILE IT'S TANGIBLE!
(I am still waiting for my 5004P after 2.5 years....:-(
Larry