I'd wager to guess that most would chose the Porsche. I know I did. You can see mine, which happens to be a 1973 911E as Paul chose for his article, here: http://www.octanenation.com/custom/1973-porsche-911/254/
OctaneNation is my startup.
Further evidence that the 911 is desirable: http://www.hagerty.com/valuationtools/HVT/VehicleSearch/Repo...
Mine sold for around $10.5k in 1973, and Haggerty says the average value now is $54k. Using an inflation calculator says $10.5k is equivalent to $53k today... Interesting.
The same Hagerty valuation tool shows the Cadillac is worth around $8k.
If that were true then why would cadillac let that model/style die out unlike porsche with the 911?