If you had to choose one which would it be? Personally, it's a tough decision for me but I believe I would take the Ferrari.
Re: Ferrari 512s or Porsche 917k? For me also it would be a very hard decision... They both attract me very much...
Re: Ferrari 512s or Porsche 917k? Yeah. Both companies had 25 made of each so they could pass regulations and be direct rivals for one another. The Porsche won Le Mans in 1970 and had a Daytona win. The Ferrari also had a Daytona win in 1971 I believe. Today the 917k is valued at $2,000,000 to $3,500,000 dollars with the Ferrari not far behind.......but you'll see a lot more Porsche 917k's at vintage races than Ferrari 512Ms.
The Porsche may be faster/more successful, but I'd still take the Ferrari. This is the most beautiful racecar ever (except maybe the Ferrari 330 P4), and I'm sure the scream of that V-12 beats the turbo-whine of the 917's flat six...